EDAX Phoenix Training Course –Introductory Diagrams - page 1

EDAX Phoenix Training Course –Introductory Diagrams - page 1

EDAX Phoenix Training Course - EDS Instrumentation & Signal Detection - page 1

ENERGY DISPERSIVE X-RAY SPECTROMETRY--EDS INSTRUMENTATION & SIGNAL DETECTION

ALAN SANDBORGEDAX INTERNATIONAL, INC.

1. X-Ray Detectors:

The EDS detector is a solid state device designed to detect x-rays and convert theirenergy into electrical charge. This charge becomes the signal which when processedthen identifies the x-ray energy, and hence its elemental source.

The X-ray in its interaction with solids, gives up its energy and produces electricalcharge carriers in the solid. A solid state detector can collect this charge. One of thedesirable properties of a semiconductor is that it can collect both the positive andnegative charges produced in the detector. The figure below shows the detectionprocess.

Figure 1.

There are two types of semiconductor material used in electron microscopy. They aresilicon (Si) and germanium (Ge). In Si, it takes 3.8 eV of x-ray energy to produce acharge pair, and in Ge it takes only 2.96 eV of energy. The other properties of these twotypes will be discussed later in this section. The predominant type of detector used isthe Si detector, so it will be favored in the discussions. With a Si detector, an O K x-raywhose energy is 525eV will produce 525/3.8= 138 charge pairs. A Fe K x-ray willproduce 6400/3.8= 1684 charge pairs. So by collecting and measuring the charge, the

EDAX Phoenix Training Course - EDS Parameters - page 1

Important EDS ParametersCount Rate

For a good quality spectrum (i.e. good resolution and fewest artifacts) you should use the50 or 100 us time constant (pulse processing time) with a deadtime of 20 to 40%, and 500to 2500 cps.These are good numbers if the sample consists largely of high energy peaks (>1 keV), but if the spectrum is dominated by low energy peaks (< 1 keV) then a count rate of500 - 1000 cps is better and the 100 us time constant should be used.

When maximum count throughput is required, such as when collecting fast x-ray maps, afaster time constant (2.5 to10 us) should be used with a count rate of 10,000 to 100,000cps. The deadtime should not exceed 50 to 67%. These conditions may not be optimum forlow energy peaks in terms of their resolution and/or position. A lower count rate and slowertime constant should be and/or it might be necessary to adjust the position of the ROI priorto collecting the map.

Accelerating Voltage

The overvoltage is a ratio of accelerating voltage used to the critical excitation energy of agiven line for an element. Typically, the overvoltage should be at least 2 for the highestenergy line and no more than 10 to 20 times the lowest energy line of interest. We use thenumber 10 for quantitative applications and the 20 for qualitative applications.

For example, if you are interested in analysis of a phase containing Fe, Mg and Si and wantto use the K lines for each, then 15 kV will probably work reasonably well. If, however, youneed to analyze the same three elements plus oxygen as well, then you might use 5 to 10kV, but you might want to use the L line for the Fe.

Why should the overvoltage be at least 2 for the highest energy element? Because at lowerovervoltages the fraction of the interaction volume where the element can be excitedbecomes very small and you will not be able to generate very many x rays of that energy.

Why should the overvoltage be less than 10 to 20 times the lowest energy peak? When theovervoltage number is excessive, the proportion of the interaction volume for which the lowenergy x rays can escape without being absorbed also becomes small. The result is asmall peak and in the case of the quantification there will be a strong absorption correctionwhich will magnify the statistical errors in our analysis.

Take-Off Angle

Typical take-off angles will range from 25 to 40 degrees. This angle is a combination of thedetector angle, its position, sample working distance and sample tilt. The sensitivity for verylow energy x rays and/or signals characterized by high absorption can be enhanced byincreasing the take-off angle. Some inclined detectors (e.g. a detector angle ofapproximately 35 degrees above the horizontal) do not require sample tilt. Horizontal entrydetectors require that the sample be tilted to achieve an optimum take-off angle.

EDAX Phoenix Training Course - EDAX Detector Geometry - page 1

EDAX Detector Geometry

The elevation angle (EA) is the anglebetween the horizontal and the detectornormal. The intersection distance (ID) is thedistance in mm between the pole piecewhere the electron beam intersects thedetector normal. The azimuth angle can notbe shown in a cross-sectional view asshown at the left, but it is the angle asviewed from above between the detectornormal and normal to the tilt axis. Theworking distance (WD) is where the sampleis in mm below the pole piece. The take-off

angle (TOA) is the angle between the x-ray trajectory and the sample surface. If the sample isplaced at the intersection distance and not tilted, the take-off angle will equal the elevation angle.

If the working distance is shorter thanthe intersection distance, the take-offangle will be less than the elevationangle. This assumes that the sample issmooth and not tilted.

If the working distance is longer thanthe intersection distance, the take-offangle will be more than the elevationangle. Again, this assumes that thesample is smooth and not tilted.

If the sample is tilted toward the detect-or, the take-off angle will be greaterthan the elevation angle. If the samplewere tilted away from the detector, thetake-off angle would be less than theelevation angle. Note that the azimuthangle must be taken into account todetermine the take-off angle.

EDAX Phoenix Training Course –Dead Time & Time Constants - page 1

Dead Time & Time Constants

In an EDS system the real time (or clock time) is divided into live time and dead time. Thelive time is the time when the detector is alive and able to receive an x-ray event (i.e. thetime when it is doing nothing) and the dead time is when the detector or preamplifier isunable to accept a pulse because it is busy processing or rejecting an event(s). Basically,the charges from an x-ray photon can be collected in about 50 ns and in the end we will takeroughly 50 us to process the filtered, amplified pulse (1000 times longer). Quite often, x-rayphotons will come in too close to each other and we will reject the signals. That is why wecan see the situation that we actually collect very few x-ray events at very high count ratesand we actually process more counts when we use a lesser count rate.

If we decide to take less time to process the pulse in the end (say, less than a 10 us timeconstant or pulse processing time) then we can process more counts. However, becausewe have taken less time, there is the possibility that we do not process the peak energy asaccurately and the peaks will be broader; the resolution will be poorer or higher.

The Phoenix system has 8 time constants or pulse processing times which will allow foroptimum resolution or x-ray count throughput. Under most circumstances, we would like tohave a dead time that is between 10 and 40% and perhaps between 20 and 30% if we wouldlike to tighten the range of our analytical conditions. There are times when we are mostconcerned about the count throughput and are not concerned about resolution, sum peaks,etc., such as when we are collecting x-ray maps. Under these conditions a dead time ashigh as 50 to 60% is feasible. Under no circumstances should a dead time that is more than67% be used because we will actually get fewer counts processed.

A series of plots are included on the following pages. These show: the fall-off in processedcounts when the count rate is increased too high, a comparison in throughput between a fasttime constant and a slower time constant, and a plot showing the dead time % for variouscount rates and time constants, and a plot of count rate versus dead time % for each of the 8time constants.

EDAX Phoenix Training Course - Spectrum Interpretation & Artifacts - page 1

EDX SPECTRUM INTERPRETATION AND ARTIFACTS

Continuum X Rays

As a result of inelastic scattering of the primary beam electrons in which the electronsare decelerated and lose energy without producing an ionization of the atoms in thesample, continuum x rays are formed. The continuum x rays are the background of ourEDS spectrum and are sometimes referred to as the bremsstrahlung. In theory, thecontinuum can be expected to extend from the maximum energy of the primary beamelectrons and increase exponentially to zero keV energy. In reality, the backgroundgoes to zero at the low end of the energy spectrum due to absorption by the detectorwindow, the detector dead layer, and the gold layer. The intensity of the continuum isrelated to both the atomic number of the sample as well as the beam energy. Thecontinuum intensity also increases with beam current.

Characteristic X Rays

Inelastic scattering events between the primary beam electrons and inner shell electronswhich result in the ejection of the electron from the atom within the sample and may leadto the formation of a characteristic x ray. The ejection of the electron leaves the atom inan ionized, excited state and permits an outer shell electron to move to the inner shell.Because the energy levels of the various shells are related to the number of charges inthe nucleus, the energy of the emitted x ray is “characteristic” of the element. The beamelectron must have an energy greater that is just slightly greater than the energy of theshell electron (the critical ionization energy).

Depth of Excitation

Although electrons may penetrate to specific depths within a sample which can beillustrated with a variety of equations or with Monte Carlo programs, the electronsactually lose energy in steps as they go to greater depths in the sample. As a result, anelectron may soon lose a sufficient amount of its energy such that it can no longer excitecharacteristic x rays. Typically, this occurs when its energy drops below the criticalionization energy of the elements in the sample. Each element within the sample willhave its own critical ionization energy and its own excitation depth. The ratio of theprimary beam energy to the excitation energy of the element is referred to as the

EDAX Phoenix Training Course - Peak ID - page 1

EDAX Phoenix Peak IdentificationThe basic procedure for identifying peaks in the EDS spectrum is not always agreed upon.Some users start with the biggest peak, identify it and all associated peaks, and thenprogress to the smaller peaks in sequence until all are identified. When there are L- and M-series peaks present, it may actually be better to identify the highest energy alpha peak firstbecause this peak may be associated with several other higher energy peaks as well as oneor more of the lower energy peaks. Then, the user can find the next lowest energy peak,etc., until all peaks have been accounted for. Another significant aid for peak ID is to clickon the button for the automatic peak ID. The results of the automatic peak ID should beinspected and verified; it very often will provide the correct answer, but the user should beaware that its answer might be only a part of the solution and that more investigation may berequired. In all cases, however, it is essential to look for escape peaks for the peaks ofgreatest height and for sum peaks for these same peaks when a high count rate has beenused for spectrum acquisition.

Typically, we examine that part of the spectrum that ranges in energy between 0 and 10 keVand we quickly become aware of characteristic features of K-, L- and M-shell x-ray peaksthat aid us in our peak identification. In this energy range, we can see peaks with K-shell x-rays that correspond to atomic numbers 4 through 32, L-shell peaks that range from roughlyatomic numbers 22 to 79, and M-shell x rays ranging from 56 to the highest known andobservable atomic numbers. For many elements it is possible to observe peaks from morethan one shell in this energy range (it is often desirable to inspect the region between 10 and20 keV as well for confirmation of lower energy peaks). The resolution of the peak of oneelement from an adjacent atomic number is often better resolved by using higher energypeaks (see spectrum of Ni and Cu below).

Peak ID Quiz -- page 1

EDAX Peak ID Quiz –“sp_pkid” SpectraOn the floppy disk provided with this notebook is a directory “sp_pkid”. This directorycontains a series of spectra “pkidXX.spc” and “deconXX.spc”. The spectra pkid01 throughpkid04 and pkid06 are the same spectra used for illustrations in the “Peak Identification”discussion. Other spectra on the disk can be used as a peak identification quiz and theyrange in difficulty from relatively easy to impossible. In the space below, identify the peak byelement and shell (e.g. SiK, PbM, SnL, etc.).

Quiz:

PkID05.spc (easy). Between 1.5 and 12 keV, the peaks are:

PkID05b.spc (easy). Between 3.7 and 7.5 keV, the peaks are:

PkID07.spc (moderately hard). Between about 0.9 and 18 keV, the peaks are:

PkID08.spc (moderate). Between 0.6 and 14 keV, the peaks are:

PkID09.spc (hard). Between 0.55 and 15 keV, the peaks are:

PkID10.spc (easy to moderate). Between 0.2 and 10 keV, the peaks are:

EDAX Quiz on Peak ID - page 1

EDAX Peak ID Quiz –“sp_pkid” SpectraOn the floppy disk provided with this notebook is a directory “sp_pkid”. This directorycontains a series of spectra “pkidXX.spc” and “deconXX.spc”. The spectra pkid01 throughpkid04 and pkid06 are the same spectra used for illustrations in the “Peak Identification”discussion. Other spectra on the disk can be used as a peak identification quiz and theyrange in difficulty from relatively easy to impossible.

Quiz Answers:

PkID05.spc. This spectrum shows a series of K-series peaks with atomic numbers 14, 16,18, 20, 22, 24, 26, 28, 30, and 32 (Si, S, Ar, Ca, Ti, Cr, Fe, Ni, Zn, Ge). There is goodseparation of the Ka peaks and the Kb peaks are easily seen. The L-series peaks are not sowell resolved.

PkID05b.spc. A similar spectrum to PkID05 except that this shows a K-series peak for everyatomic number between 21 and 27 (Sc, Ti, V, Cr, Mn, Fe, and Co). In this area of thespectrum the Kb peak of a given atomic number is overlapped by the Ka of the next higheratomic number. Note the non-resolution of the L-series peaks for the same atomic numbers.

PkID07.spc. This spectrum is an older, non-Sapphire spectrum; that is why you will get thedialog box asking if you want to “ignore”, “cancel” etc. From 1 keV to 18 keV, the peakspresent are:

ZnL, (NaK?), MgK, AlK + BrL, Si, NbL (probable), MoL, ClK, K K, TiK, V K, CrK, MnK,FeK, CoK, NiK, CuK, ZnK, BrK, MoK.

PkID08.spc. Between 0.6 and 14 keV, the peaks are:NiL, SeL, ZrL, PdL, TeL, TiK, NiK, SeK.

PkID09.spc. Between 0.55 and 15 keV, the peaks are:F K, TaM, ThM, TaL, ThL. (This spectrum might also have some Uranium and other

radioactive elements).

PkID10.spc. Between 0.2 and 10 keV, the peaks are:C K, CrL, NiL AlK, SiK, MoL, TiK, CrK, FeK, CoK, NiK. (There is probably also some

CoL in the sample but it is not a resolved peak).

PkID11.spc. Between 1 and 10 keV, the peaks are:P K, InL.

PkID12.spc. Between 1 and 10 keV, the peaks are:S K, CdL.

Decon01.spc. Between 1 and 10 keV, the peaks are (or might be):IrM, P K, ZrL, InL, IrL.

Decon01b.spc. Between 1 and 10 keV, the peaks are (or might be):Y L (?), IrM, P K (?), ZrL (?), InL, SnL, IrL.

EDAX Training Course - X-Ray Count Optimization - page 1

THE OPTIMIZATION OF X-RAY COUNT THROUGHPUT

The x-ray count rate is certainly one our most fundamental parameters for determiningoptimal spectrum conditions. It is counter-intuitive for most users that increasing thecount rate does not automatically result in a better spectrum or at a minimum incollecting more counts. The EDAX detector amplifier has two time constants (20 µs and40 µs) which control the amount of time taken to process an x-ray event. While the xray is being processed, the detector is “dead” and will not process any additional events.For each time constant there is a maximum throughput. When it is desirable to havemore counts in a spectrum or in a map, it is always possible to collect the signal for alonger interval of time, but it is also possible to use a shorter time constant. When theshorter time constant is employed, the spectrum resolution degrades but for manyapplications this is not a serious drawback.

The figure below provides an example of how many counts can be processed in a fixedinterval of time (20 clock seconds). With the longer time constant (“40 tc” or 40 µs),there are actually fewer counts processed when the count rate was increased from 2000to 10,000 cps. The same 10,000 cps count rate yielded 6 to 7 times more processedcounts when the shorter time constant (“20 tc” or 20 µs). With the shorter time constant,doubling the count rate only increased the processed counts by about ¼.

The resolution of the detector degrades noticeably when using the longer time constant(see figure on the next page), but resolution is not normally a fundamental concernwhen we do certain procedures such as collecting x-ray maps, or when the spectracollected do not have significant overlaps and we are not concerned with low-energypeaks or their analysis.

EDAX Basic Procedures- SEM Quant ZAF 1

SEM QUANT ZAF

Geometry The EDX detector parameters are specific for each microscope. The

elevation angle, intersection distance, azimuth angle, and scalesetting must be known and understood for microscope/detectorgeometry. Before collecting a spectrum, an accurate acceleratingvoltage should be verified and the working distance and take-offangle must be accurate. Every microscope has an optimized geometryor an optimized range of conditions. If spectra are collected thatare not correctly specified, then the subsequent quantification willnot be accurate and comparisons to spectra collected under differentconditions will be difficult at best. Also, spectra collected froma non-optimal geometry are subject to more stray radiation artifactsand possibly to a reduced count rate.

Every detector comes with a blue Detector Specification Manual.This manual contains blueprints for the detector and gives all thepertinent parameters (working distance, intersection distance, etc.)that need to be entered into the Geometry dialog in the EDAM panel.

Enter the kV reading from the microscope in the EDAM panel (buttonlocated in the upper right corner of the screen).

Select a time constant (Amp Time) in the EDAM panel. Longer timeconstants (100 usec, 50 usec, and 35 usec) are typical settings forspectrum collection.

Setup PresetPredefined collection times can be created in the Setup: Presetdialog box found in the Setup pull-down menu.

Spectrum Collect, Erase, Save To start collecting a spectrum click on the stop watch button (far

left). To stop collection do the same (click on the stop watch button (far

left). To clear a spectrum click on the paint-roller button next to the

stop watch. To save the spectrum click on “File: Save As...”.

Follow the usual procedures for saving any file in MS Windows.The spectrum files will normally (default) be saved to theD:\edax32\eds\usr sub-directory. Another path can be chosenhere.

The “Save As” dialog box will select the first set of charactersfrom the spectrum label for the file name prefix. There is a128-character limitation to the filename as defined by MicrosoftWindows ’98 and NT.

The default file type his as a “.SPC” file suffix, but the filetype can also be changed to save the spectrum as a graphic file(.BMP or .TIF) to be inserted into MS Word or other reportwriting software.

Labels and Add Text Up to 216 characters can be saved as a spectrum label. The sample

label is displayed at the top of the spectral window in the “A:”labeled box or, if it is an overlaid spectrum, in the “B:” labeledbox. The sample label can be edited directly by clicking in the “A:”or “B:” labeled boxes above the spectrum or by selecting Label fromthe Edit pull-down menu.

Text can be added to the spectrum by selecting “Add Text” from theEdit pull-down menu.

EDAX Basic Procedures- Imaging/Mapping 1

Imaging/Mapping

Image Collect/External XYTo collect an image:

1. Confirm that the kV and Magnification are correctly enteredinto the “IMG” panel. When Column and Stage control are notavailable these two parameters will have to be enteredmanually. Press the ENTER key after entering each parameter.

2. Put the microscope into external scanning mode. Eachmicroscope has its own procedures to allow the externalcontrol of its scan circuits. Depending upon the age of themicroscope an enable button may need to be pressed on a thirdhardware box or the microscope may have to be put into anexternal mode in the microscope software. For newermicroscopes the EDAX system will automatically take control ofthe beam when the “e-“ button is clicked. To confirm thatEexternal scan is activated the “Ext XY” button will turnyellow (active) in the Imaging/Mapping software and themicroscope screen will blank or freeze with an image.

3. Once these are correctly displayed in the image panel click onthe “e-“ button or select “electron image” from the “Collect”pull-down menu.

To improve the image quality, click on the "IMG" control panelbutton and increase the matrix size to decrease pixelation effects.Re-collect the image by clicking on the "e-" button again. Typicalimages are collected at 512x400 or 1024x800 matrix sizes. The “Strips” box denotes the number of times the screen will be

updated during the image acquisition.Integrated Frames

To decrease the "grain" or noisiness of the image, increase thenumber of integrated frames (IntF) by “wiping” or by clicking anddragging the mouse over the number in the “IntF” box and entering anew number. This is located in the lower half of the Img panel.

Spectrum Collect and QuantificationTo collect a spectrum, the screen display should be set to displaythe spectrum and image (the button shows both and is found just tothe left of the “e-“ button). A current image should be displayed. Spot scan in the Imaging/Mapping software should be selected ("+"

button found in the button bar at the top of the screen). Clear any existing spectrum (Click on the paint roller button). Position the cursor on the area of interest in the image

displayed and click the mouse. Start collecting the spectrum (Click on the stopwatch button). Identify the peaks using the Peak ID control panel just as is

done in the ZAF32 program. When the peaks are of adequate size and quality, stop the

spectrum collection (Click on the stop-watch button again). To improve the spectrum display, you can click and drag on the

spectrum to stretch it both horizontally and vertically. Thebuttons above the spectrum are used just as in the ZAF32 program anda text label can be entered just above and to the right of thespectrum (press the "enter" key following the label text entry.

To quantify a spectrum, click on the “Q” button in the button bar ofthe spectrum area. The quantification results appear in the upperright section where the histogram of the image is displayed. Thisquantification is a standardless quantification.

EDAX Basic Procedures- Line Scan

The EDAX Line Scan option in the Imaging/Mapping software program allows the user todefine a line for data collection, collects dataalong that line, then opens a Microsoft Excelspreadsheet containing the results (netintensities, weight percent concentrations, andatomic percent concentrations). Thisspreadsheet can be manipulated in MicrosoftExcel to create line graphs. The followingapplication note is designed to walk the userthrough these steps and provide a few tricks tomake these line scans look professional.

Collecting Line Scan DataTo collect a line scan in the Imaging/Mappingprogram capture an image from themicroscope. Collect a spectrum from the areaof interest and identify the elements. Set upregions of interest from the element list.Once elements and ROI’s are defined the linescan can be collected.1. Open the Line scan panel and click on the

line button .2. Draw a line across the area of interest on

your image by clicking and dragging themouse.

3. Choose a dwell time that allows enoughtime to collect valid data (This isdependent upon count rate.)

4. Select the number of collection pointsalong the line.

5. Click on the Line scan button, “L”, andenter a name for the data to be savedunder.

6. Click on OK and the line scan will begin.

When the line scan is complete an Excelspreadsheet should be opened containing allof the acquired data.

**Tip: If you stop a line scan during thecollection be sure to close the Excelspreadsheet that is created before beginningthe line scan again.

Creating a Line Scan in Microsoft ExcelHighlight the columns and rows of informationyou wish to graph.

**Tip: Choose elements that are close inconcentration so that the scaling allows fornicely displayed line graphs. This may requirecopying columns of data from the originalspreadsheet and pasting into a new sheet.

Once the data is selected:1. Click on the Chart Wizard button in the

toolbar or select “Chart” from the “Insert”pull- down menu.

2. Choose line graph from the options of graphtype.

3. Setup procedures will prompt you through theinitial creation of your line scan. During thesesteps you can label the line scan, define theX and Y axes, and create a legend.

4. Once these parameters have been chosenclick Finish for a look at the general format ofyour line scan.

Sample XYZ

00.5

11.5

22.5

3

1 66 131

196

261

326

391

456

Wt %

AlK Y L TiK

Advanced Line Scan ProceduresThe line scan above is a quick and easy creationusing Microsoft Excel. However, correlating theline scan and image can be difficult without theimage in the background of the line scan. Thefollowing procedures are provided in the MicrosoftExcel Help section.

Add a picture to a chart itemUse this procedure to add a bitmap to the chartarea, the plot area, and the legend in 2-D and 3-Dcharts.1. Double click on the plot area to open the

Format Plot Area window.2. Click on the Fill Effects button, select the

Picture tab, and click on Select Picture.3. Imaging/Mapping automatically saves the

image with the line scan location to the folderyou designated before starting the line scan.

4. Click on OK to exit the Format window.

**Tip: Line scans display best when collectedfrom left edge to right edge.

Sample XYZ

0

0.5

1

1.5

2

2.5

1 53 105

157

209

261

313

365

417

469

Wei

ght % AlK

SiK TiK

Line Scan (option)

EDAX Basic Procedures- Multi Point Analysis 1

SEM Multi Point Analysis

Spectrum Collect Near the upper left of the screen are the “Start” and “Clear”

buttons. Once the Start button has been clicked and the acquisitionhas begun the button becomes a “Stop” button.

The spectra can be saved under the “File” pull-down menu.Peak ID

Click on “ID” from the menu bar will provide a peak ID panel (whichcan be removed by clicking on “R”) which will do an “Auto” peak ID.Elements can be highlighted from the “Elem List” and deleted(“Del”). The “Z-” and “Z+” keys will move up and down the periodicchart by atomic number. If the goal is to identify a specific peakin the spectrum, then click the right mouse button on the peak andlook at the suggestions in the “Possible” list box.

Standardless QuantificationIf the spectrum has been collected for a good length of time(approximately 100 Live seconds for statistical accuracy) and allelements are identified then by clicking on the “Conc” in the menubar at the top of the screen will apply a standardlessquantification on the spectrum. The results will appear in aspreadsheet dialog box. These results can be printed, translatedinto graphs, and save from this dialog box.

Image CollectTo collect an image click on “e-” (to indicate an electron image) inthe button bar and it will collect from the SEM. This image is afrozen image and will not reflect any changes you have made to theSEM from the Microscope Control software unless you refresh theimage by clicking on the “e-” button again. The image can be savedunder “File”, “Save as...” and specifying “.BMP” from the list boxand then giving a file name. During subsequent analysis there maybe a variety of graphics superimposed on top of the image which willbe saved with the image if it is saved at that point.

Multiple Point AnalysisIn the menu bar, there is a choice “Loca - X” where the X can beeither an S for spot, an L for a line or an M for a matrix. It ispossible to select any of these 3 in the pull-down menu.

To select spots for analysis, the image must be displayed (seeabove), the menu bar should indicate “Loca-S”, and the mouse shouldbe clicked on the image at the point of interest. Then the “S”button from the button bar should be clicked to save that location.More points can be added by clicking on the image and clicking on“S”.

Similarly, if lines have been selected and the menu bar nowindicates “Loca-L”, you can click and drag on the image to define alinear array of points for analysis, then click on “S”.

For a matrix of points, click and drag a box to define the matrixand then click on “S” to save these locations.By default, the line will do 10 points per line and the matrix willbe a 2 X 2 matrix of points. To change either of these, click on“Loca- “ and “Table...”, then highlight the number you want tochange, and strike the enter key.

To display the locations on the image, click on “Loca - “ and clickon the listing to display the locations or to display the locationswith their numbers at the bottom of the pull-down menu.Before beginning the multi-point analysis, you should be sure that:

EDAX Basic Procedures- Spectrum Mapping 1

Spectrum Mapping (option)

Collecting Spectral MapsIt is recommended that the following conditions be set up beforecollecting a spectrum map:

The detector geometry should be correct. (Setup: kV & Dist) The count rate, dead time, and time constant should be setup for

high throughput (counts per second), 20-40% dead time, and a timeconstant to allow for the other two parameters. Typically with ahigh count rate the time constant will be short, eg. 2.5, 4, 6.(Setup: EDAM & Calib)

An image and spectrum of the area to be mapped should be acquiredand the elements of interest identified.

With this complete the setup for Spectral Mapping can begin. Click on SpcMap in the Multi-point Analysis menu bar. The Spectral

Mapping dialog window will open. Enter a dwell time. This is dependent upon the count rate. A dwell

of 200 msec is acceptable for a count rate of 3000 cps. A shorterdwell time can be used if the count rate is higher. Likewise, alonger dwell time should be used with a lower count rate. Theobject is to dwell at each pixel long enough to collect sufficientdata for analysis.

Select a matrix size. The resolution of your maps will have asignificant effect on the total acquisition time.

Highlight the extension in the file name and enter four charactersother than Abcd.SPZ. Press the Enter key on the computer keyboardwhen you finish typing in the new name.

Confirm that the SPZ and 10 keV boxes are checked. These arecompression formats that decrease the size of the spectral map file.

Check the Estimated Time for the maps (displayed below the filename)to confirm an acceptable collection time.

Click on the START button. The system will begin to acquire the data, dwelling at each pixel.

When the collection is complete the system will beep. To build the maps, click on the Build Map button. (Note that even

though you have maps displayed at this point they are not saved orretrievable without being built.) A window will display anestimated time for the processing of the data if it is estimated totake more than two minutes. Choose YES.

Displaying MapsTo view the maps:

Click on the Show Map button. Select the folder of interest and highlight one of the maps. Click OPEN. All maps in the folder will be opened for viewing. Toggle on the up and down arrows to flip through the maps in the

folder. Check the Color box to convert the image to a color scale. The warm

colors indicate high intensity while the cool colors indicate lowerintensities.To view multiple maps:

Click on the Adv button. Highlight the maps you wish to view. To select more than one, hold

the control button down and select maps with the cursor. Click on the View Multiple Maps button. The maps selected are

displayed to the right.

EDAX Basic Procedures-

Spectrum Utilities

IntroductionVery few customers may be aware of anextremely handy program that is part of yourEDAX system. The Spectrum Utilities programcan typically be found on the C drive, in theUtilities folder of the EDAX programs. Itsexecutable file is abbreviated to SpecUtil.exe.

SpecUtil was created to allow the user to printmore than one spectrum on a page. In fact,SpecUtil is formatted to fit 10 spectra on asingle 8.5’ x 11’ page. This feature is veryhelpful when a large volume of spectra arebeing compiled for a report or for archivingpurposes. Programs that might benefit fromthis capability are particle analysis, GSR (gunshot residue), and multi-point analysispackages.

Procedures for Printing Multiple Spectra1. Select File:Open from the menu bar and

locate the file folder that contains thespectra you would like to print.

2. Select any one of the spectra from thefolder and click on the OPEN button. Allthe spectrum files in that folder will appearlisted in the left column of the SpecUtilwindow.

**Note This means all spectra meant to beprinted on the same page must be located inthe same folder.

3. Hold down the control button and selectthe spectra to be printed.

4. Click on SPC>>Printer in the menu bar.

**Tip: The arrow buttons will manipulate theview of the spectrum. These should be usedto prepare the spectra for printing. **Note:The view settings you chose will be applied toall of the spectra when they are printed.

**Tip: The spectra can be printed in black andwhite, color outline, or color solid by togglingthrough the Print Display button to the left ofthe Printer button.

Previewing SpectraTo preview a spectrum double click on its name inthe list.

For viewing multiple spectra before printing beginwith steps 1-3 of the printing procedures then doas follows:

4. Turn off the printer option by clicking on theprinter icon (a red X should appear over theicon).

5. Select a viewing speed by adjusting the scrollbar.

6. Click on the SCA>>Printer to begin thepreview.

Changing the HeaderThe page header can be personalized by going toHelp: Intro and entering a new label.

Displaying Particle Images with SpectraWhen a CSV data file type is selected fromFile:Open Spectrum Utility has the added abilityto read in a Particle & Phase Analysis datasets.Selecting a CSV dataset will display all thespectra from a single or multi-field run.

With a particle data set active, other optionsbecome available at the bottom of the applicationswindow.• Analysis location coordinates can be burned

into new BMP (Loca*.Bmp) files.• Particle images can be inserted into the upper

right hand corner of each correspondingspectrum area on printouts.

Spectrum Utilities

EDAX Training Course - Quantitative Analysis - page 1

Quantitative X-Ray Analysis using ZAF

Spectra collected with the DX system can be analyzed to provide weight and atomicpercent data. Standards can be used for this analysis or the sample may be analyzedwithout standards (i.e. “standardless”). In either case, the procedures are very similarand will be discussed below.

Figure 1. Spectrum of an aluminum-chromium-nickel alloy collected at 15 kV.

When many users attempt to interpret an EDS spectrum, there is often a tendency toinfer weight percent from a visual estimate of the peak height and this usually leads toerroneous interpretations. For instance, in the spectrum in Fig. 1, the Cr peak is about 1½ times larger than the Ni peak which is about 2 ½ times larger than Al peak. Whereas,the correct analysis actually has the Ni being about 1 ½ times the Cr and the Ni is justabout 20 times more abundant by weight percent than the Al. Even experienced micro-analysts who have an extensive knowledge of overvoltage and absorptionconsiderations would be reluctant to infer relative weight percents from a spectrum suchas this.

The correct interpretation of a spectrum would actually be to compare an element’speak height to the height of the pure element collected under identical conditions.

EDAX Training Course - Analysis with Compound Standards - page 1

--Quantitative Analysis with Compound Standards

INTRODUCTION

The primary purpose of this discussion is concerned with how to use standard(s) in quantitativeanalysis using the ZAF or eDX software. Even when standardless quantitative analysis isroutinely performed, it is always a good idea to obtain a standard of a similar composition andsee how close the standardless analysis is to the reported data. If it is desired or necessary toimprove the accuracy of the analysis, then standards can be used to accomplish this.

The examples discussed below utilize a sample set of 6 mineral spectra (a garnet standard; thespectra are labeled garnet01.spc to garnet06.spc). The garnet01.spc has been implementedas the standard to analyze the remaining 5 spectra which have been collected from differentspots on the same standard. Quantitative results are summarized for analyses using the“Compound Standard” mode, and with the use of SEC factors (Standardless ElementCoefficients).

THE COMPOUND STANDARD

The spectra to be analyzed will typically have been collected from a single session in sequenceusing the same element list, with the same accelerating voltage, and with the same beamcurrent/spot size setting. It is possible to compensate for variations in beam current if a currentmeter and Faraday cup are available, but this is primarily of value if the user can not be certainthat the analyzed elements should have a sum which equals 100% (or very near 100%). In thiscase, an assumption for the garnet standard of 100% for the reported elements (O, Al, Si, Ca,Mn and Fe) is certainly valid.

Procedure. In the ZAF or eDX software, open the standard file spectrum (garnet01.spc; clickon “File”, “Open” and specify the file name from the correct directory). The first step will be toprovide the information necessary that will allow us to use this spectrum as a standard.Although, the sample is an oxide, oxygen will be measured directly as an element; and thissample was saved with oxygen in the element list and oxides were not checked as the sampletype.

In the space below, mouse clicks will be shown with brackets with the text enclosed within todesignate the button or feature where the mouse is clicked. For example, “[OK]” indicates thatthe mouse is clicked on the “OK” button.

-the “Quantify” control panel should be made active.-[Stds]

-[Options]-[Compound]-[Setup]-Type the percentage for each element followed by an “enter” (38.78, 10.92, 17.08, 0.24, 15.35, and 17.64 for the O, Al, Si, Ca, Mn, and Fe, respectively)-[RZAF] (calculated pure element intensities will be displayed)

EDAX Training Course --Analysis with Pure Element Standards - page 1

--Quantitative Analysis with Pure Element Standards

INTRODUCTION

The pure element standards method requires that a series of pure element standards becollected under constant conditions (same geometry, kV, and beam current into a Faradaycup). The constant conditions does not mean that they should have the same dead time or thesame absorbed current while on the standards because both parameters will vary with theatomic number and possibly with overvoltage considerations. Probably the dead time shouldnot be more than 30-40% on the sample or standard with the highest dead time.

THE PURE ELEMENT STANDARDS SETUP

Procedure. In the ZAF32 software, open the first standard file spectrum (”std15ala.spc”; clickon “File”, “Open” and specify the file name from the correct directory). If there is a questionabout “save existing spectrum”, click on “No”.

Before we start creating a pure element intensity table of elements based upon our directmeasurements, it will be a good idea if we verify what parameters are associated with our table.In the Quant. control panel, click on “Stds” and then on “Pure”. Then you should click on“Factors” in the Quant. control panel and verify that the detector type is correct (probably“SUTW” and “Sapphire” for most of you) that the method is “ZAF”, and that the voltage iscorrect (15 kV in this case).

In the space below, mouse clicks will be shown with brackets with the text enclosed within todesignate the button or feature where the mouse is clicked. For example, “[OK]” indicates thatthe mouse is clicked on the “OK” button.

-the “Quantify” control panel should be made active.-[Stds]

-[Options]-[Pure]-[Setup], it will show the measured pure element intensity-[Save]

-[Yes]-[OK]

Then open the next spectrum (”std15cra.spc”) and repeat the steps above, followed by the lastof the three pure element standards (”std15nia.spc”) and repeating the above steps again.When all are entered, then you are ready to begin processing your unknown samples. If youwould like to confirm that everything is as it should be, click on “Factors” in the Quant. controlpanel and verify that Al, Cr, and Ni have values that are not 1. Also, the detector type shouldmatch your samples (“SUTW” and “Sapphire” in this case) and that the method is “ZAF”.

If all standards have been processed, it would be a good idea to save a standards file. Click on“File” and “Save as…”, select the STD file type and give the file a name (e.g. “alcrni15.std”).The standards file saves a list of all elements, their shell (K, L, or M) and their pure elementintensities. If an element does not have pure element data associated with it, it has a recorded

________________________________________________________________________EDAX Training Course –Quantitative Analysis with SEC Factors - page 1

Quantitative Analysis with SEC factors --Hans DijkstraFor microanalysis the composition of a sample can be calculated from the measured X-rayintensities using:

Where Z, A and F are the matrix correction parameters, describing the atomic number effect(stopping power and backscatter effect), the absorption effect, and the fluorescence effect.

Since for standardless analysis we have no ΙSTD available, EDAX has chosen to use calculatedstandards, with in a simplified form:

I n p f NAR

Q EdE d s

dECalculatedStd

d j jlj

E

E j====

ΩΩΩΩ4

0

0ππππ

εεεε ωωωω χχχχρρρρ

( )( )/ ( )

Where n is the number of electrons entering the sample, Ω/4π is the solid angle, ε is the detectorefficiency, ω is the X-ray fluorescence yield, p is the relative probability for the transition involved,f(x) is the absorption correction, and the integral represents the cross-section of the ionizationinvolved. Since n is unknown, and thus set to 1, the calculated intensity might be in a totallydifferent order of magnitude as the measured intensity. Normalizing the W% to 100% solves thisproblem.

This function seems to work rather accurate, but it is important to notice that some factors are leftout of the calculations, like the solid angle, since this is a constant factor and this equation is onlyused for standardless analysis, i.e. the results are normalized to 100% anyway.

One disadvantage of this equation is that εd, the detector efficiency, can not be predicted withsufficient accuracy for X-ray lines below 1 keV. Small variations in detector quality (Si dead layer,etc.) can cause variations in measured intensity. Therefore EDAX has introduced the SEC factors.The final equation now becomes:

The SEC factors can simply be calculated by entering a compound standard, and calculate the SECfrom the given W% (thus the ZAF factors and the standard intensity can be calculated) and themeasured intensities. Also in this procedure calculated SEC factors may be off by an order ofmagnitude, and now this is solved by assuming one SEC factor to be identical to a default value(thus keeping it fixed), and scaling other SEC factors relative to the fixed one.

W Z A F II

Meas

Std% ==== •••• •••• ••••

W Z A F ISEC I

Meas

CalculatedStd% ==== •••• •••• ••••

••••

EDAX Phoenix Training Course - Introduction to Digital Imaging - page 1

Introduction to Digital Imaging

Digital images are defined by the number of pixels (picture elements) in a line across theimage, by the number of lines and the number of colors or gray levels in the image. Thenumber of gray levels is usually expressed in bits (8, or 12 bits) which is the exponent usedwith the number 2. An 8 bit image has 256 levels (0 - 255), and a 12 bit image would have4096 (0 - 4095). At each a pixel a number is stored to represent or color or gray level. Inmost imaging programs on the PC, the ‘0’ value represents black, the highest valuerepresents white and the intermediate values are shades of gray.

As illustrated in the above figure, our work with images can be thought of as being imageprocessing if we start with an image and if the result is an image. The image is processedor enhanced; perhaps sharpened, or the contrast is modified. Image analysis would involveany operation in which we start with an image and the results of the operation are numbersor data.

A portion of a digital image is shown below. This is an 8 bit grayscale image which consistsof 32 pixels per line and 32 lines of data. As with all digital images, the image can bezoomed to the point where the pixels become obvious. The four images at the below leftshow the same number of pixels shown with a different zoom factor.

It is possible to view the actual numerical data for the image. A profile of pixel values areshown below for a horizontal line across the middle of the eye.

52 36 26 25 71 114 126 128 149 176 182 90 27 45 51 62 50 68 48 40 39 29 99 126 68 36 35 30 39 45 57 77

EDAX Phoenix Training Course - PhotoImpact - page 1

EDAX Phoenix Procedures – PhotoImpact

Introduction

PhotoImpact is an image processing program that provides many additional featuresnot available in the Phoenix imaging software. This program is comparable in manyways to Adobe Photoshop and has a manual, training software, as well as on-linehelp to describe many detailed procedures that can be implemented using thissoftware. In x-ray microanalysis and electron microscopy, there is really only a smallsubset of its capabilities that most of us will ever need. It is intended that thefollowing few pages will describe those procedures to enable the user to use thisprogram without having to become an expert on image enhancement software.

PhotoImpact actually consists of several programs. Four of the programs that will bementioned at least briefly here are:(1) PhotoImpact, a basic image enhancement program that is most similar to

Photoshop;(2) PhotoImpact Album, a program that allows the user to create thumbnail images,

to print multiple images on a single page and to create a slide show of images;(3) PhotoImpact Capture, a screen capture program which is a fairly simple program

that will not be described in detail here;(4) PhotoImpact Viewer, a simple image viewing program which can be set up in the

Explorer to be the program opened when you double click on an image file –it isthe program that the Album program opens when you double click on a thumbnailimage.

Most of the PhotoImpact programs will allow you to open multiple files. Once animage is opened it is possible to zoom it by clicking on the “+” or “-“ keys. Also, mostoperations can be undone (Ctrl-Z) and re-done (Ctrl-Y).

Procedures

In all procedures below the text shown in brackets represents a mouse click (e.g.“[OK]” would indicate a click on the “OK” button). Tabs are used to show thehierarchy of commands (i.e. a menu bar selection is shown to the left, with oneadditional tab to indicate a click from the pull-down menu, and an additional tab toshow a click from the resulting dialog box, etc.).

Most steps in image enhancement can be undone if it is decided that the result wasnot optimal. This is accomplished by clicking on “Edit” and “Undo”. The shortcut toundo an operation is Ctrl-Z and Ctrl-Y will re-do the same operation. There aremultiple levels of undo for an image and the number of undo’s can be specified byclicking on File and Preferences. The higher the number of undo’s that you specifywill be more memory intensive. It is possible, or a good idea to save a modifiedimage with a new name to protect yourself from lost data when there are lengthyimage processing protocols.

To Open an Image

EDAX Training Course -

Report Writing with Microsoft Office

It is often desirable or a requirement to create reports that integrate text interpretation with data(spectra, quantitative results, images, etc.). MS Word and MS Excel are readily available wordprocessing packages that can be used to prepare such a report.

The spectral data in any EDAXapplication is typically stored withthe file extension .SPC. These filescan be stored from, and recalled toEDAX applications only. When thegoal is to store a spectrum thatcan be inserted into a Wordreport, the spectrum should besaved as a BMP or TIF file.

** Note When saving the spectrumas an image it will be saved as itappears in the spectral window ofthe ZAF program. Therefore, ifthere is an area of interest the usershould click and drag that area intoview before saving. Figures 1-3demonstrate this feature.

The spectrum, as an image file, canthen be inserted into the Worddocument easily. Drawing a “textbox” in MS Word and inserting thepicture into the box will determineits size and location. The threefigures to the left were inserted thisway, as was this text on the right.The black outlines of the text boxeshave been left visible todemonstrate this technique.• To insert text into these boxes

simply click with the cursorinside of the box and startwriting.

• To insert an image in a text boxposition the cursor in the boxand select Insert: Picture:From File.The images can be previewedin this dialog box, the desiredimage chosen, and insertedinto the document.

Figure 1 Entire spectrum saved as image file.

R

“Text boxes” canbe directly addedto the graphic.The text box colorand border can bemodified bydouble clickingwithin them.

Figure 2 Low end of spectrum saved as image.

ep

Figure 3 Peaks of interest saved as image file.

ort Writing with MS Word - page 1

EDAX Phoenix Training Course - Summary - page 1

SummaryParameters

Typical parameters for good resolution (spectrum dominated by peaks with energies greater than1 keV) with the fewest artifacts:

--kV > 2X highest energy peak--Time Constant = 50 or 100 us--Deadtime = 20 to 40 % (adjusted by changing count rate)--Take-off angle = 25 - 40 degrees--Working distance = intersection distance (for inclined detectors)

When the spectrum has significant peaks with energies less than 1 keV, the parameters should bethe same as above except that the count rate should be 500 to 1000 cps. When the sample is tobe mapped, the same parameters should be used except that a count rate of 10,000 to 100,000cps (10 to 2.5 us time constant) should be used in order to improve the statistical quality of themap. This assumes that the sample will tolerate the heat caused by the higher beam currents,that the larger spot sizes do not degrade the resolution of the image or maps, and that the verylow energy peaks are not of primary interest which usually require lower count rates and a longertime constant.

Artifacts

Escape Peaks = keV of parent peak - 1.74 keV (Silicon Ka energy).Sum Peaks = 2X energy of the dominant peak in a spectrum, or

the energy of peak A + peak B when two peaks are dominant.Stray Radiation or “System Peaks” = Peaks derived from the pole piece, stage,

sample holder or detector window support. These are usually moresignificant with horizontal EDS detectors.

Peak ID

Auto Peak ID will usually be adequate when the spectrum is dominated by K-series peaks. Whenthe spectrum contains several L- or M-series peaks, the best strategy may be to manually identifythe highest energy alpha peak and observe what other low-energy peaks are also associated withit. Then continue with the next highest energy alpha peak and continue until all are identified.

Quantification

Whether the quantification involves the use of one or more standards, or if it is a standardlessanalysis, the procedure is the same: the peak intensities are calculated apart from thebackground; the peak intensities are compared to intensities of the pure elements to calculate thek-ratio; and corrections are made for atomic number (Z), absorption (A) and fluorescence (F).When standards are used, the pure element intensities are actually measured, but these can becalculated when no standard is present. The ZAF corrections assume that the sample/detectorgeometry is well known, that the sample is smooth, and that it is homogeneous. If theseassumptions are accurate, then the quantitative results will also be accurate.

To Create and Save an Anaglyph Color Stereo Image with Photoshop

This procedure assumes that you have created and saved the two images from which you wantto create and save a color stereo image. Typically, these two images will differ in tilt by 5 to 10degrees and will have been collected at a eucentric working distance if one is available. Sampleswith a lot of surface topography (e.g. fibers or needle-shaped crystals) will require less tilt thanrelatively flat samples. The resulting stereo image will require a pair of red-cyan glasses to viewthe color anaglyph image. These glasses have a red lens for the left eye and a cyan lens for theright eye. Red-green glasses can also be used.

Commonly, the stereo images will be collected with a minus 90 degree scan rotate. In order forthe stereo pair to have the correct parallax, the tilt axis should be vertical on the display. Theimage collected at a lower tilt can be saved with a number after a file name indicating the tilt atthe end of the file prefix (or an "r" or "red" to indicate which image this is in the pair), and thehigher tilt image saved as well with the tilt indicated (or a "c" or "cyan" included in the file name).The two images that make up the stereo pair will be named "fracred.tif" and "fraccyan.tif" forinstance.

Ideally, the eucentric working distance, or the point where image registration occurs will belocated at a mid-height position in the sample. This permits a maximum amount of topography tobe portrayed in the resulting stereo image. Those portions of the sample that are at the eucentricposition will show no color shift between the two images and will appear to be grey or have nocolor because the two images are in registration and the red and cyan sum to a neutral grey.Areas of the anaglyph image that appear to be "up" in the image will have the red image shown tothe right of the cyan. Those areas of the stereo image that appear to be "down" will have the redimage shifted to the left of the cyan image. When the amount of shift becomes too excessive, itbecomes difficult for the brain to "fuse" the two images. This will occur if an excessive amount oftilt differential is applied to a sample with normal topography or surface roughness.

Creation of the Color Anaglyph Image in Adobe Photoshop

Two methods will be discussed for creating a stereo pair. Method II is probably the simpler of thetwo. These procedures have been used and tested in versions 3 and 4 of Photoshop.

Method I:

1. The two images that will make up the stereo pair should be recalled from disk using thenormal procedure for recalling files ('File', 'Open', and then selecting the appropriate file type,directory and file name). In version 4 you can select both images by clicking on the first oneand then a Ctrl-click on the second image from the file list.

2. The cyan image should now be duplicated by clicking on the cyan image to make it the activeimage (i.e. the title bar above the image should be blue), followed by clicking on 'Image','Duplicate...', and clicking 'OK' to accept the default image name for the duplicate.

3. The next step below will require the use of the "Channels" palette or box. If this box shouldappear on the monitor, you should skip to step number 4. If this box can not be seen, clickon 'Window', 'Palettes', and 'Show Channels'.

4. In the Channels palette box there will be some text near the top of the box that reads"Layers", "Channels" and "Paths". If "Channels" is not already highlighted, you should clickon it and then click on the right-facing triangle to its right (>); then click on 'MergeChannels...'. For "Mode" you should select 'RGB Color' with the channels equaling "3", thenclick on 'OK'. In the "Merge RGB Channels" dialog box you should assign the red or lower tilt

To Create a Stereo Image, page 2

image to red and assign the cyan image and its duplicate to the green and blue channel, thenclick 'OK'.

5. An untitled RGB color anaglyph stereo image should now appear on the monitor. Prior tosaving the image, the contrast and brightness should be checked and adjusted if necessary.This can be done most easily with the "Adjust Levels" procedure which is implemented with a"Ctrl-L". This will bring up a dialog box that has a histogram and adjustors for black, themidtone and white. These adjustors are immediately below the histogram and they should beadjusted to provide an optimum image on the monitor. As a general rule, it probably makessense to slide the black adjustor to the beginning of the left side of the histogram, and thewhite to end or to the right side of the histogram --this should be approximately equivalent toclicking on 'Auto'. The image displayed should be updated to reflect these changes --if it hasnot, this probably means that the "Preview" box has not been checked. If the resultant imageappears to be too light, then you should move the midtone adjustor to the right. If the imageis too dark, the midtone adjustor should be moved to the left. The midtone adjustment ismost equivalent to the gamma function of the SEM. When you are safisfied with theappearance of the image, click on 'OK'.

6. To check the 3D image, put the anaglyph glasses on (red for the left eye and cyan for theright eye) and see if the topography appears normal. If it does, proceed to step 7.Depending upon how the original images were collected or saved, it may be that the colorswill have to be re-assigned or the glasses reversed. Also, if the tilt axis is not vertical in thetwo images as displayed, it may be necessary to do a 90 degree rotation of the image at thistime (click on 'Image' and 'Rotate' and chose a clockwise or a counter-clockwise rotation of90 degrees.

7. The color stereo image can now be saved by clicking on 'File' and 'Save As...', or by a "Ctrl-S". The file can be saved in a variety of formats, but the most common are probably the TIFFor JPEG. If saved as a TIFF, the resulting file will be approximately 1 MB or three times thesize of the original standard definition XL SEM file. If saved as a JPEG with a "High" imagequality setting, the file will probably be about 1/4 to 1/6 of the size of the TIFF depending onthe level of fine detail in the image.

Method II:

1. The two images that will make up the stereo pair should be recalled from disk using thenormal procedure for recalling files (“File”, “Open”, and then selecting the appropriate filetype, directory and file name). In version 4 you can select both images by clicking on the firstone and then a Ctrl - click on the second image from the file list.

2. Convert the higher tilt image (the cyan image) to an RGB color image by clicking on “Image”,“Mode”, and “RGB Color”. Display the red channel by pressing a “Ctrl – 1”.

3. Activate the lower tilt image by clicking on the image. This image should be converted to agrayscale image if it is not one already by clicking on “Image”, “Mode”, and “Grayscale”.

4. Select the entire image with a Ctrl - a and then copy it to the clipboard with a Ctrl - c.5. Re-activate the higher tilt image with its red channel actively displayed, and then paste the

image from the clipboard with a Ctrl - v.6. Display the entire color image with a Ctrl - ~. At this point you can modify the image and/or

save it to disk just as in steps 5 – 7 in Method I above.

Bob AnderhaltEDAX Applications Laboratory

June 17, 1999

EDAX Training Course - Report Writing w

Another common file format supported by EDAX applications is the CSV format (commaseparated values). Results files and summary tables are typically saved as CSV files. Spectracan also be saved in this format. This is actually a text format that is most commonly used toinput data into a spreadsheet program from which it can be plotted or have additional calculationsmade. Portions of that spreadsheet file can be highlighted and copied to the clipboard and pastedinto the Word report directly (see below) or into a text box.

Stainless Steel Wt%

18%2%

62%

14% 3%1% SiK MoL CrK MnK FeK NiK

Inserting Quantitative Results into aReport

1. In MS Excel• Click and drag to highlight the information

to be copied.• Select Copy from the EDIT pull down

menu.

2. In MS Word• Draw a text box or position the cursor

where the results should appear• Select Paste from the EDIT pull down

menu.

Advanced Options

• Highlight the columns of the table• Select Table Autoformat from the Table

pull down menu• Choose a style• Click OK

Graphs and charts created in MS Excel can alsobe copy and pasted into an MS Word document.

Element Wt % At %

SiK 0.75 1.48 MoL 2.58 1.5 CrK 17.89 19.14 MnK 1.72 1.74 FeK 63.4 63.18 NiK 13.67 12.96 Total 100 100

Element Wt % At %


Element Wt % At %


ith MS Word - page 2

EDAX Training Course - Report Writing with MS Word - page 3

The report can also include the BMP or TIF files from x-ray maps or electron images. Just as withany BMP file, they can be inserted by clicking on “Insert”, “Picture” and the file names provided asusual.

Fig. 1. BSE Image of an aluminum Fig. 2. Aluminum x-ray map. alloy fracture surface.

After inserting the first image (Fig. 1), the cursor is shown at the lower right of the image. Bypressing the space bar a few times before doing the next insert, the second image will appear tothe right of the first but on the same line. After Figure 2 was inserted, the Enter key is pressedtwo times to provide some space between the first and a possible second row of images. Thisarea can also be used for labeling the images.If the x-ray maps had been collected at lesser resolutions, it would have been possible to placemore than two of them on a single line. Alternatively, it would also be possible to resize eachimage by clicking on it and adjusting one of the corners. For multiple images, the percentage ofenlargement should be noted, so that it can be reproduced on each additional image of the series.

a. BSE b. Phosphorus c. Silicon d. Titanium e. Carbon f. Oxygen

When creating a template document where the images may not have been collected yet, or arebeing collected at the same time as the report is being generated, the text-box feature in MSWord is handy. The steps for inserting a text-box are the same described on the previous page.Inserting an image or pasting an image can be done right into the text-box. This is also usefulwhen handling large images and maps as a standard image insert would occupy a large portion ofthe page. The images below have a 1024x800 resolution and have been reduced to fit the size ofthe text-box.


The eDXAuto/Multi-Point Analysis software package provides integrated imaging with automatedanalysis including line scan and multi-point analysis features. Some of the graphic overlays on animage are shown in the four examples below. Each image is saved as a BMP file when the imagearea appears as shown. The image is refreshed (to Fig. I below) by clicking on “Image” and“Display Current”. Images are inserted in Word the same as described previously. It is possibleto overlay more than one line scan on a single image, but the data are usually communicated bestwith a single line scan. There is a direct printout in which all line scans are printed in sequence ona single page.

I. Sandstone image area (BSE). II. Image with 14 multi-point locations.

III. Silicon linescan along blue line. IV. Calcium linescan.

The results of a multi-point analysis are provided by eDXAuto as a summary table that can behighlighted and copied to the clipboard. It is then pasted into Word where it can be highlightedand a font size selected to fit the page. Important samples and analysis locations can behighlighted by underlining them or by making them boldface or a larger font. In the example onthe following page, a table title and caption were added to the summary table.


Table 1. Results of multi-point analyses from mineral sample. The samplelocations with high iron concentrations are shown in boldfaced type and italics.

DxAuto Results Summary : C:\DX4\AUTO_P\USR\SSA101.SMY 05-27-1997 17:07:44KV: 20.0 Tilt: 0.0 TKOff: 36.8Wt%: C K O K NaK MgK AlK SiK P K K K CaK TiK FeK

Notessa101 3.57 54.51 0.15 0.00 0.24 40.43 0.63 0.11 0.10 0.07 0.20ssa102 9.38 53.54 2.08 6.59 2.96 8.42 0.11 0.41 12.91 0.20 3.39ssa103 19.32 46.58 0.24 7.96 0.51 1.39 0.36 0.74 19.29 0.14 3.47ssa104 21.95 32.84 1.29 0.65 12.22 19.25 0.79 7.72 0.64 1.21 1.44ssa105 8.68 53.46 0.33 5.33 1.70 2.27 0.30 0.78 15.78 0.07 11.31ssa106 3.95 48.55 0.45 0.17 8.68 26.93 0.15 10.34 0.13 0.19 0.48ssa107 8.87 53.82 0.37 5.83 0.17 0.23 0.14 0.23 19.73 0.16 10.46ssa108 14.31 46.41 0.55 5.41 3.43 3.97 0.60 1.12 14.63 0.00 9.57ssa109 9.98 54.75 0.38 8.55 0.49 0.68 0.21 0.24 18.45 0.18 6.09ssa110 10.19 46.35 4.32 0.72 7.35 21.43 0.15 0.09 3.53 0.00 5.85ssa111 4.36 48.05 0.38 0.18 8.69 26.91 0.18 10.39 0.16 0.16 0.55ssa112 3.99 48.25 0.51 0.21 8.87 26.78 0.52 10.29 0.00 0.11 0.46ssa113 4.07 47.94 0.43 0.18 8.77 27.08 0.53 10.48 0.16 0.06 0.30ssa114 16.59 39.00 1.36 0.85 19.50 14.87 0.80 3.92 1.07 0.41 1.64ssa115 4.16 48.21 0.19 0.18 8.67 27.05 0.45 10.58 0.26 0.05 0.19

The ability to interface with standard desktop publishing, spreadsheet, and image enhancementsoftware is primarily permitted by the use of three universal file formats (BMP, TIF, and CSV).This ability is further enhanced with graphics overlays on the image and by cutting and pasting tothe Windows clipboard. Thus providing an easy working environment for the user.

**NoteThis table cannotbe changed usingthe Autoformatbecause it waspasted as text.


Procedure-[File]

-[Open]

Select the correct drive and directory according to normal Windows conventions.Under File types, it is possible to select “All Files”, “BMP”, “TIFF”, or 25 other imagefile formats. It is possible to double click on a single file to view it in PhotoImpact, orto click on the first file of interest and then to Ctrl-click on additional images and thenclicking on “Open” to activate multiple images. Similarly, clicking on the first file froma set of images, followed by a Shift-click on the last image from the set will allow youto “Open” all images from that set.

Changing Brightness & Contrast

Setup. An image should be open and active in PhotoImpact. To open an image,see procedure described above.

Procedure-[Format]

-[Brightness & Contrast]

Click on the thumbnail with the most optimal brightness and contrast. Repeat ifnecessary, then [OK]. An alternative is shown below:

-[Format]-[Tone Map]

Click on the “Highlight Midtone Shadow” tab. Optimize the image with the sliders,then [OK].

To Change Image Mode

Images collected in the Phoenix imaging software will be “palette color” images (256colors) if it was an x-ray map or if it was an electron image. In order to print an imagewell or to perform an image processing operation, it is often necessary to change animage/map to either a gray-scale image or an RGB color image. With the image thatyou want to change open in PhotoImpact and active, [Format], [Data Type] and thenclick on the desired file type (typically, “Grayscale” or “True Color”. Note that thecurrent image type will be gray-ed out and not selectable.

To Create a 3D Anaglyph Image from a Stereo Pair

Setup The 3D anaglyph image contains two images, one which is shown in red andthe other is either green or blue-green (cyan). When viewed with the correspondingcolor glasses, each eye sees a different image where the differences in the imagecorresponds to a difference in tilt or perspective, and our brain reconstructs a 3-dimensional image just like it normally does.


It is assumed that you have a stereo pair on disk that it has been recalled toPhotoImpact. The two images should have the same pixel dimensions (e.g.512x400, or 1024x800) and they should differ only by their tilt. Also, the tilt axisshould be vertical on the monitor with the SE detector on the left (on many SEMs thiswill require a -90 degree scan rotate). If the conditions for the two images aredifferent than just described, you may need to depart from the procedure describedbelow (i.e. the color designation may need to be changed, and/or the merged imagemay need to be rotated). In PhotoImpact the 3D image is created using a CMYK(cyan, magenta, yellow, black) merge function. One image will be assigned to cyan,the other to both magenta and yellow (this makes red) and a white image with novideo information will need to be created and assigned to the black channel.

It will be helpful when saving the two original images to denote the tilt of each image,or to append a letter for the color of each image (e.g. an “r” for the red image and a“c” for the cyan image).

Procedure

The two images should be converted to grayscale images; [Format], [Data Type] and[Grayscale]. You may need to keep a note as to which image is the lower tilt imagebecause the conversion process will create a new image called “Untitled X” where “X”is a sequence number. When both images have been converted to grayscale, then itwill be necessary to create a white image with the same definition (512x400 or1024x800, for instance) as the two images that differ in tilt. To create a new imagethat is completely white:

-[File]-[New]

A dialog box will appear, and you should ensure that the data type is grayscale (8-bit), the image size matches the resolution of the two images (512x400 or 1024x800,for instance), then [OK]. If the image is a white image, you are ready to proceed. If itis not white that is most likely because the background color has been selected to besomething different. In that case, click on the background box under the grayscalepalette at the right side of the screen; then enter 255 for each of red, green and blue.

When the two images have been converted to grayscale and the white image isavailable:

-[Format]-[Data Type]

-[Combine from CMYK]

A dialog box appears. In PhotoImpact (different from several other imageenhancement programs) you should assign the lower tilt image to cyan, the higher tiltimage to both magenta and yellow, and the white image to the black channel, then[OK].

Check the resultant image with your glasses (red for the left eye, cyan for the righteye). If the image does not work, see note at the end of the second paragraph of


this section (i.e. the color designation may need to be changed, and/or the mergedimage may need to be rotated). To determine if the image needs to be rotated, turnyour head sideways to see if the 3-dimensionality improves. If the image has whatshould be down as up (and vice-versa), then switching the glasses around will help toclarify this situation; this indicates that the original color assignments of the twoimages were incorrect.

The anaglyph image can be saved as an RGB or true color TIFF or BMP file. It canalso be saved as a JPG file. This is a compressed type of file that will take up lessroom on disk but can show some degradation in image quality. For stereo colorimages, saving a JPG file with a “Quality” setting of 75 to 80 (found from the “SaveAs…” dialog box under “Options…” if JPG is the file type) will provide an imagewithout significant degradation and a file that is typically 1/10 the size of the originalfile. A series of these 3D images can be put into an album file (see a followingsection) and played as a slide show.

To Overlay Text on the Image

Procedure The image to be annotated should be displayed on the screen. The texttool should be activated by clicking on it (the “T” button next to the bottom of the left-hand tool bar). The bar above the image will show the font, its size, style, color, etc.By clicking on the active areas, it is possible to change the selection. To place texton the image:

-With the text tool active, click on the image area where you would like the text to appear.-Type the text in the dialog box.-You may click on “Update” to see the text on the image or [OK].-If you would like to re-position the text, place the cursor on the text and drag the text to another location.-The font, size, color, etc. can be changed while the text is still active.-To deactivate the text, you may push the space bar or [Edit], [Object], and [Merge].

You are able to type additional text entries by repeating the steps above

To Overlay a Spectrum on the Image

Procedure The image to be annotated should be displayed on the screen. Thespectrum to be overlain should have been saved as a BMP file from the ZAFsoftware and also recalled into PhotoImpact. Because the spectrum is a solid color(assuming that the spectrum “Page Setup” dialog box was not set to “Outline” mode)that is different from the spectrum background, it will be possible to cut and paste itinto another image using what is commonly called the ‘magic wand’ tool. This tool isselected by first clicking on the third button from the top –it looks a little like a magicwand with an irregular dashed line around it. The bar above the image area will showsome options for the magic wand tool and the most important may be the “similarity”number. It can probably any small number (<10) for this application.

Place the cursor for the magic wand tool on top of the spectrum area of the BMP file.A marquee should be seen which encloses the spectrum and shows that the


spectrum area is active. Next, the spectrum should be cut or copied to the clipboardand pasted into the image:

-[Edit]-[Copy]

Activate the image that you want to paste the spectrum into (i.e. click on it, or click on“Window” and select the image from the list at the bottom of the pull-down menu.Also, if you are going to paste the spectrum as a color image, then you shouldconvert the gray-scale image to a true color image first; [Format], [Data Type], [TrueColor]. To copy the spectrum:

-[Edit]-[Paste]

Click and drag on the pasted object to position it where you would like it. Whenyou are satisfied with its position, you should deactivate the text by pushing the spacebar or [Edit], [Object], and [Merge].

At this point you might want to use the text feature in PhotoImpact to add text to labelthe peaks. It would have been possible to copy the peak labels from the originalspectrum file by using the magic wand tool to click on each letter, but this is tediousand time consuming. Also, when the spectrum is shown on the image, it has to standout from the detail in the image. The file can be saved with the overlay.

To Create Thumbnails of the Images and other Album Procedures

Procedure-[File]

-[New]

A dialog box will appear that gives a choice of templates, but it will probably be bestto use the “General Purpose” template. Type a title (e.g. “Maps”), then [OK]. Fromthe “Insert” dialog box select the correct directory, then click, ctrl-click, shift-click orclick and drag on the image files of interest, the [Insert]. You can chose an additionaldirectory and repeat the insertion procedure from the previous sentence. To finishthis session [Close].

You can add additional thumbnails to an existing album file (or group of thumbnailimages) by [Thumbnail] and [Insert]. The will bring up the same dialog box as in theprevious paragraph.

Other Album Procedures. If you double click on any thumbnail image it will open upthe Viewer program and show you the image. The image can be zoomed by hittingthe “+” or “-“ keys. The slide show program can be implemented by first selecting thethumbnails of interest (or Ctrl-A to select all), then [View], [Slide Show], then selectthe appropriate options and [Play]. The slide show can repeat continuously, or justplay once and terminate, or it can be terminated with the escape key.


EDAX Phoenix Training Course - Introduction to Digital Imaging - page 2

The brightest part of the eye has a gray level of 182 and the darkest part of the eye has agray level of 26. An image processing operation could be used to stretch or increase thecontrast. If this were done, the range of gray levels could be increased to as much 0 to 255as shown at the bottom of the preceding page at the right.

The previous image is an 8 bit, grayscale image. Other types of images can be only 1 bit(sometimes called a bitmap) which consists of black or white pixels, 256 color paletteimages (8 bits but it can contain a variable array of colors), 24 bit color images (sometimescalled RGB or true-color images). The 24 bit color images contain 8 bits (256 levels) eachof red, green and blue.

Image files tend to be very large files. An image that is 1024x1024x8 bits is 1 megabyte insize, and 512x512x8 bits would be 250 kilobytes. If an image is stored as an RGB cololrimage, it will take 3 times as much disk space. The EDAX digital image file sizes are 3.2megabytes (2048x1600x8 bits), 800 kilobytes (1024x800x8 bits), 200 kilobytes (512x400x8bits) and decrease by a factor of 4 for each smaller image size.


value of “1”. The standards file only contains a table of pure element intensities, it does notactually save a spectrum.

PROCESSING THE UNKNOWN SPECTRA

For the sake of consistency in this lab, click on “Results” and make sure that ”Intensity” and“%Conc” are both checked. Then click on “Options” and make sure that there are checksplaced by “Methods”, “At%”, “K-Ratios”, “Wt%”, and “ZAF”, and that there is no check at thistime next to “Multiple”. There are 7 spectra that were collected from an alloy consisting ofaluminum (3.0 Wt%), chromium (38.5 Wt%), and nickel (58.5 Wt%). These spectra are labeled“alloy15a.spc” to ”alloy15d.spc”, and ”all15a.spc” to ”all15c.spc”.

To quantify any of the alloy samples recall them from disk and click on “Quantify” from theQuant. control panel. The data can also be shown non-normalized by clicking on “Type”,“Option”, removing the check next to “Normalization”, “OK”, and clicking on “Quantify” again.

At this point, each analysis is shown as a single table with the element, Wt%, At%, K-Ratio, Z,A, and F shown from left to right, and the elements shown from top to bottom by increasingenergy. Another table will follow will give intensity data. If the goal is to accumulate multipleresults (done by checking “Multiple” next to the “Quantify” button), then there will be severalrepetitions of these tables with the most recently acquired results at the bottom of the listing.

It is possible to reformat the multiple results table by clicking on “Results” (near the top of thecontrol panel), then on “Options”, and placing a check mark next to “Mult. Results”, then “OK”.Now, the multiple results table will be formatted with the elements shown from left to right andthe sample number from top to bottom. There will be a series of tables for “Weight % byElement”, “Atomic % by Element”, “K-Ratio”, etc. If the results table is saved as a CSV file aftermultiple analyses have been performed, this file can be brought into MS Excel and additionalmathematical operations can be performed (averages, standard deviations, and sums). Such atable has been copied to the clipboard and pasted into Word below.

Given Weight % 3.0 38.5 58.5Weight % by ElementFilename AlK CrK NiK Total ALL15A.SPC 3.05 37.82 58.04 98.91 ALL15B.SPC 3.12 37.44 58.15 98.71 ALL15C.SPC 3.40 37.96 57.97 99.33ALLOY15A.SPC 3.26 37.39 58.70 99.35ALLOY15B.SPC 3.07 38.24 57.90 99.21ALLOY15C.SPC 3.24 37.56 58.42 99.22ALLOY15D.SPC 3.18 38.86 57.21 99.25

Mean 3.19 37.90 58.06 99.14Std. Dev. 0.11 0.52 0.47 0.22

Saving a Compound Standard as a Pure Element Table


It is often desirable to use a compound standard together with several additional pureelement standards. Of course, the same analytical conditions must apply to the pure elementstandards as well as to the compound standard (same analytical geometry, same beamcurrent, voltage, etc.). In the example below, we will use one of the samples from theprevious exercise (“alloy15a.spc”) as a compound standard. Just as in the case above, weshould first verify that the parameters for our pure element intensity table is correct byclicking on “Stds” and “Pure”, then clicking on “Factors” and verify that the detector type,method and voltage are all correct.

-the “Quantify” control panel should be made active if it is not already active.-[Stds]

-[Options]-[Compound]-[Setup]-Type the percentage for each element followed by an “enter” (3.0, 38.5 and 58.5 for the Al, Cr, and Ni, respectively)-[RZAF] (calculated pure element intensities will be listed in the dialog box)

-In this case, you should leave the “Use as compound” checkbox unchecked-[OK]

-[Save][Yes]

-[OK]

At this point, the calculated pure element intensities will be listed in the pure element table andthe standards type will be listed as “pure”. This standards file could be saved as in the caseabove by clicking on “File” and “Save as…”, select the STD file type and give the file a namefollowed by an “Enter”. If another pure element standard were available (Mn or Fe for instance),it would be possible to add them to our table by following the procedure above ([Stds],[Options], [Pure], [Setup], [Save], [Yes], [OK]).

Using this procedure it is possible to merge data from multiple pure element spectra and a pureelement standard. It is even possible to use multiple compound standards. It may be a goodideal to take some notes of the pure element intensities calculated for each standard because itis likely that an element might be present in more than one standard. The table will record thelast standard value that was saved and it might be best to use one of the previous values or anaverage of several standards. The pure element intensity values that can be viewed by clickingon “Factors” may also be edited to reflect your choice.


-[Use as compound]-[OK]

-[OK]

At the completion of this procedure, the compound standards button should be checked, andwe are ready to re-call our spectra to be analyzed against this standard. You may wish toselect “Multiple” results in order for you to more readily compare these data. Recall eachspectrum ([File], [Open], specify “garnet02.spc”, [OK], and [No] to save the changes to theprevious spectrum if you do not want to save it). At this point, you only have to [Quantify] andyou will see your results. An additional spectrum can be recalled and the same procedurerepeated. See Table 1 for a summary of the results for the analysis with standards as well asthe standardless data.

In order to use this compound standard in a subsequent session, you should save aquantitative methods file (QZF). Cick on “File”, “Save as…”, select the QZF file type and givethe file a name followed by pressing the “Enter” key. There is a standards file type (STD) butthis is reserved for the table of pure element intensities that result from the use of pure elementstandards.

SEC FACTORS

SEC factors are Standardless Element Coefficients. Even though it is said to be standardless,it is possible to use a standard to derive these factors and the resulting quantitative data arevery nearly as good as data generated from analysis with standards. To maximize the qualityof the results, the same accelerating voltage, the same matrix type (as close as possible)should be used, and the same set of elements should be present in standard and sample.

Procedure. The “Quantify” control panel should be open for these steps and the sample to beused to develop the new set of SEC factors should be open (in our case, “garnet01.spc”).

-[Stds-[None] if this was not already checked.-[Options]

-[Compound]-[Setup]-Type the percentage for each element followed by an “enter” (38.78, 10.92, 17.08, 0.24, 15.35, and 17.64 for the O, Al, Si, Ca, Mn, and Fe, respectively)-[SEC]

-[Update SEC Table]-[OK]

-[OK]-[SEC]-[User]-[File] from the menu bar

-[Save As…]-Change file type to .SEC and type “garnet” and hit the enter key (this will save the SEC factors for the next time similar samples are to analyzed)


At the completion of this procedure, these new SEC factors will be available for use. We areready to re-call our spectra to be analyzed against these factors. You may wish to select“Multiple” results in order for you to more readily compare these data. Recall each spectrum([File], [Open], specify “garnet02.spc”, [OK], and [No] to save the changes to the previousspectrum if you do not want to save it). At this point, you only have to [Quantify] and you willsee your results. An additional spectrum can be recalled and the same procedure repeated.See the SEC results at the bottom of Table 1. The error values are comparable to, and actuallyslightly better than the data for the analyses with the compound standard. It is expected,however, that the compound standard procedure should be a more robust procedure when wedepart even slightly from the ideal conditions of this test because it is based more soundly upona more rigorous, “first principles” approach.


Table 1. Garnet analyses for the same spectra when analyzed with no standards(“NoStd”), with a compound standard (“Stndrd”), and with SEC factors (“SEC”) derivedfrom the same standard that was used for the compound standard.

Garnet Analyses

Carbon Coating Correction = 9

NoStd Filename O Al Si Ca Mn Fe

GARNET02.SPC 38.77 11.83 17.1 0.37 14.48 17.45GARNET03.SPC 38.39 12.00 17.36 0.30 14.51 17.44GARNET04.SPC 38.70 11.82 17.35 0.36 14.61 17.15GARNET05.SPC 38.40 11.89 17.40 0.35 14.50 17.46GARNET06.SPC 38.75 11.92 17.36 0.33 14.28 17.37Mean 38.602 11.892 17.314 0.342 14.476 17.374Std.Dev. 0.19 0.07 0.12 0.03 0.12 0.13%CV 0.49 0.59 0.69 8.77 0.83 0.75Reported 38.78 10.92 17.06 0.24 15.35 17.64%Error -0.46 8.90 1.49 42.50 -5.69 -1.51

Stndrd Filename O Al Si Ca Mn Fe

GARNET02.SPC 39.05 10.84 16.74 0.30 15.26 17.81GARNET03.SPC 39.07 10.88 16.91 0.30 15.19 17.65GARNET04.SPC 38.97 10.68 16.95 0.28 15.49 17.63GARNET05.SPC 38.74 10.73 16.97 0.35 15.34 17.87GARNET06.SPC 38.83 10.90 17.01 0.25 15.13 17.89Mean 38.93 10.81 16.92 0.30 15.28 17.77Std.Dev. 0.15 0.11 0.04 0.04 0.16 0.14%CV 0.38 1.01 0.25 14.20 1.06 0.78Reported 38.78 10.92 17.06 0.24 15.35 17.64%Error 0.39 -1.04 -0.84 23.33 -0.44 0.74

SEC Filename O Al Si Ca Mn Fe

GARNET02.SPC 38.95 10.85 16.77 0.30 15.29 17.84GARNET03.SPC 39.03 10.89 16.92 0.30 15.20 17.66GARNET04.SPC 38.95 10.68 16.95 0.28 15.50 17.63GARNET05.SPC 38.77 10.73 16.96 0.35 15.33 17.86GARNET06.SPC 38.87 10.89 17.00 0.25 15.12 17.88Mean 38.91 10.81 16.92 0.30 15.29 17.77Std.Dev. 0.11 0.11 0.03 0.04 0.17 0.13%CV 0.29 1.01 0.20 14.20 1.09 0.74Reported 38.78 10.92 17.06 0.24 15.35 17.64%Error 0.35 -1.03 -0.82 23.33 -0.40 0.76


Although this is commonly not an easy thing to do, the quantitative analysis actuallydoes this comparison in its calculation (this is shown graphically in Fig. 2 below).

Fig. 2. Same spectrum as in Fig. 1 (shown in solid black) compared to the outline ofthe pure element intensities for each element.

The ratio of the element’s peak height in a sample to the pure element collected underthe same conditions is actually used in the quantitative calculation as the k-ratio. Allother steps in the quantitative analysis with and without standards are identical and theonly difference is whether the pure elements are actually measured (with standards) orare calculated (standardless). Before the k-ratios are calculated, the peaks areidentified, a background is fit, a peak-fitting routine is used and overlapped peaks aredeconvoluted, and the net count intensities are measured. After the k-ratios arecalculated, the ZAF corrections are applied, where: Z is an atomic number correctionwhich takes into account differences in backscattered electron yield between the pureelement and the sample (high atomic number pure elements will produce fewer x raysbecause some of the beam electrons leave the sample before losing all of their energy);A is the absorption correction which compensates for x rays generated in the sample butwhich are unable to escape when they are absorbed within the sample (low-energy xrays tend to be heavily absorbed); and F is the fluorescence correction which will correctfor the generation of x rays by other x rays of higher energy. In order to calculate theZAF factors, the composition must be known, but we need to know the ZAF factors tocalculate the composition. This apparent contradiction is resolved by calculating ZAF


and the composition through a series of iterations until the last iteration makes noeffective difference in the result.

Table 1. Quantitative results for the spectra in Figs. 1 and 2.

Element Wt % At % K-Ratio Z A F

AlK 3.4 6.84 0.0159 1.0897 0.4277 1.0003 CrK 37.96 39.6 0.3887 0.9866 0.9911 1.047 NiK 57.97 53.56 0.5688 1.0014 0.9798 1

Total 99.343 100

The actual weight % is calculated by multiplying the k-ratio by 100% and dividing by theproduct of the Z, A and F factors (Table 1). The standardless results will always benormalized to 100%, while it is possible to provide a non-normalized result whenstandards are used.

Standards can be pure element standards (one standard for each element) or acompound standard (consisting of multiple elements) can be used. The pure elementstandard will provide the pure element intensity directly. The spectrum from acompound standard has a known peak intensity and known compositions. The ZAFcoefficients can be calculated from the known composition and the ZAF factors areapplied in reverse (RZAF) to calculate the pure element intensities.

The conditions used to collect the standard or standards and the unknown(s) must beconstant. The detector-sample geometry must be the same, the accelerating voltageused must be the same, and the beam current should ideally be the same. Themaintenance of the first two conditions as invariant is relatively simple. Slight variationsof the beam current of a few percent will cause an inaccuracy of the final analysis whenpure element standards are used. If a single compound standard is used and theresults are normalized, the results will usually still be of good quality. The quality of thestandardless analyses will not typically be affected by an unstable beam. When it isdesirable or necessary to obtain non-normalized results, the beam current should bemonitored with a specimen current meter and with a Faraday cup on the sample stageor in the microscope column. A Faraday cup can be constructed for the stage by drillinga hole into a carbon planchet or a sample stage and placing an aperture on top of thecavity. The depth of the cavity should be at least 6X the diameter of the aperture. If thebeam is placed within the opening, then all of the primary beam is captured andconducted through the meter to ground and there will be no secondary or backscatteredelectrons leaving the sample.


Recalling Spectral MapsTo open saved spectral maps for further analysis make theadjustments for the new analysis before opening the spectral mapwindow:

• To create new maps, update the element list• To create linescans, set the location marker to Loca-L.

To recall spectrum map data without reprocessing the data: Click on SpcMap in the menu bar. Click on the FILENAME button. Select one of the spectrum files (.SPZ) from the sample of interest. Click on OPEN. Click YES to load both the image and the spectra. This loads the

original image and all of the spectra associated with it. Thespectrum that appears on the screen with the image is the total ofall spectra for that image.

To view the spectral maps, click on the SHOW MAP button.Creating Spectra Load the stored data file of interest as shown above. To build spectra from the image and hidden data activate the Add Up

Spectra check box and choose Spectrum as the display type. Click OK to exit the Spectral Mapping window. The sample image is

shown with the sample spectrum. Clear the spectrum. Select Loca-spot, line or matrix. Draw on the image.• While in spot mode, click on a point. The spectrum for that pixel

will be displayed. Clicking on another will add that spectrum tothe first.

• While in line mode, draw a line on the image. The spectrum thatappears is a total of all the pixel spectra.

• While in matrix mode, draw a box. The spectrum that appears is thesum of all the pixels included in that box.The operations for spectra act as they normally would. A spectrumcan be erased and another created without reloading the spectralmapping file. This option is useful when overlaying spectra fromdifferent regions.

Creating Linescans from Recalled Data Open the stored data as shown in section 3.4 of this manual. To build linescan from the image choose Line Scan as the display

type. Click OK to exit the Spectral Mapping window. The sample image is

shown with the sample spectrum. Define the location marker as line (Loca-L). Draw a line on the on the image. The Line Scan Setup window will

open. Click on DISPLAY.Creating Quantitative Maps

Once Spectral Data has been collected it is possible to createquantitative maps. A ZAF correction is performed on each of thespectra that were saved with the image.

If the original element list is not the list of elements desired forQuantitative maps (Elements need to be added or taken away.) adjustthe element list now.

To create Quant Maps, open the Spectral Mapping file as shown inSection 3.4 of the manual.


Open the SpcMap window. Click on the BUILD QMAP button. To view the maps click on SHOW MAP. Select a map from the file.

The Quant Maps are identified with a “Q” in their filename. Click on the Color check box to change to map to a thermal color

scale. When clicking on a pixel in an element’s quant map the calculated

concentration for that element at that pixel is displayed in theinformation area below the map.

For further viewing see Section 3.2 – Displaying Maps.Print

There are three options for printing Spectral Maps, single map,image and map, and multi-color maps. Single X-Ray Map prints theactive map in the left corner of the window. Image and Map printsthe active map and the image. Multi-Color-Map prints all the mapshighlighted.

EDAX Basic Procedures- Multi Point Analysis 2

You have a valid element list for the points of your analysis (seePeak ID)

You have a preset time for spectrum acquisition (listed under“Setup: Preset & Memory”)

Your “output” options are matched to your expectations and that youhave specified three letters for a prefix for the spectra to bestored (under “Setup: Auto Output”).At this point you can click on “Auto” and “Start” and the procedurewill begin. When it is finished (you will hear music) and theresults can be examined by clicking on “Auto” and “Summary” andselecting your results file.

Linescan (option)To start a linescan:

Make sure that you have a correct element list Click on “Loca - “ and select “Line”. Click and drag a line on a current image (you do not have to press

“S” to save it). Click on “Image” and “LScan conditions...”. In this dialog box: Click on “Read position” Make sure that the number of points and the dwell time per point are

suitable Click on “Start Lscan”.

You will know when the data acquisition is finished (again, you willhear a beep). From the same dialog box, click on “Display” and youwill see the line scans for each element.In the menu bar and pull-down menus there are choices to select asingle element, to overlay it on the image, etc.

To save the linescan, close the linescan dialog boxes by clicking on“OK”, etc., and click on “File”, “Save As...” and select linescanfrom the file type list box and give it a name and save the file.You may also wish to save the image as a BMP file if you have somegraphics that are of interest.

Print “File: Print Output” opens a dialog box where the choice for

printing the image and spectrum are available. The spectrum can be printed as an outline or in solid. The half page box should be checked when printing the spectrum

and image. If only one is being printed then the full page canbe selected.

To print click on the Print button. To exit the dialog box without printing, click on OK.


Mapping (standard, live, quantmaps) The standard type of x-ray mapping requires a specified dwell time

for each pixel and collects gross intensity information from regionsof interest. Other options available include Live (this collects anumber of very fast frames and allows the user to terminate themapping session after any frame) and Quantitative maps (allows forthe collection of de-convoluted and ZAF corrected maps).

To collect maps, the area of the sample to be mapped should bedisplayed on the microscope screen, an image collected and allelements should be identified (see above). A suitable count rateshould be established with the optimum time constant (this will varywith the sample type, magnification selected, and if there are peakoverlaps which will require the best detector resolution). Open the ROI control panel and click on the “Auto” button. The

ROI control panel icon is the second button in the cluster ofpanel buttons, next to the Peak ID panel button.

Open the MAP control panel: For standard maps select a matrix and a dwell time that are

consistent with the time available (Table 1), spatialresolution (Table 2) needed and signal-to-noise required.

For Live maps select a matrix size and check the check boxnext to “live” in the MAP panel. Be sure the number offrames is set to 1024 or so.

For Quantitative maps check the check box next to “quant”in the MAP panel. Select a matrix and dwell time that areconsistent with the time available, spatial resolution(Table 2) needed and signal-to-noise required.

The estimated time for map collection will be displayed in thestatus bar at the bottom of the screen. Use this when determiningmatrix and dwell times. Note* For live maps there is no estimatedtime as the maps will collect until the user stops the collection. Click on the X button to begin the map collection. Provide a prefix for the images to be stored, then click on OK. Confirm the parameters for the map collection and click on OK.When the maps finish collecting they will automatically be saved.To recall maps use “File: Open”, choose to open an image group, anddouble click on any one of the maps saved with that filename. Allmaps and images with that base name will open.

Table 1. Length of time to complete an x-ray map in minutes orhours (shown in underlined text).

Dwell Times (ms)1 5 10 50 100

Pixel Size64x50 0.1 0.3 0.6 2.7 5.4128x100 0.3 1.2 2.2 10.8 21.4256x200 1.2 4.6 8.9 43.0 1.4512x400 4.7 18.4 35.5 2.9 5.71024x800 18.9 1.2 2.4 11.5 22.82048x1600 1.3 4.9 9.5 45.9 91.4


Table 2. Pixel size in micrometers at different magnifications anddifferent horizontal image size (pixels).

Magnification100x 1000X 10,000X

# of Pixels64 18.6 1.86 0.19128 9.3 0.9 0.09256 4.6 0.5 0.05512 2.3 0.2 0.021024 1.2 0.1 0.012048 0.6 0.06 0.006

Table 3. Time to capture 512 x 400 image. **

Int. F=1 Int. F=100 Int. F=500

1 strip 2.67 sec 4.46 sec 12.74 sec10 strips 2.98 sec50 strips 6.7 sec

** Time for 1024 x 800 image would be roughly 4 X these times.

Overlay MapsThis function creates an overlay image from up to six selectedimages and displays the result in the first empty window available.The element with the highest relative concentration in its map willbe displayed at each pixel (substitution overlay).

Select View_16 screen mode from the View menu. (The maps must be incolor for the overlays to make any sense. If they are not in color,Select “Color Palette” from the “Display” menu.)

Click on the images you want to overlay while holding the Ctrl Keypressed.

Select “Substitution Overlay” from the “Process: Color” menu.Reverse Palette

The black background of maps can be swapped to white by selecting“Reverse Palette” from the “Display” pull-down menu. This is donemainly to save ink when printing. Maps should not be initiallycollected in this display mode.

Zoom and Measure on ImageTo enable the zoom operation you have to be in View_4 or View_16screen mode.

Click the button (with a magnifying glass) from the toolbar orselect “Zoom Enabled” from the “Display” menu.

Click and drag on the image to define the area to be zoomed. (Youhave to drag to the right and down to enable the zoom operation).

A popup window will show the zoomed area. You can move the zoomwindow around by clicking and dragging it to a new location on yourscreen.

To dispose of the zoom window double click on it. To copy the zoomed area to the clipboard select “Edit: Zoom to

Clipboard” from the “Edit” menu. From the clipboard you can paste itin an MS Word document or in a selected image view. To place thezoomed image into an image view, click in a free image view andselect “Paste” from the “Edit” menu. The new image is available nowfor all image view operations (File, Print, Edit, Process or Zoom).


The line measurement tool button lies to the right of the zoombutton. Clicking on the line measurement tool will move theselected image to the 1_view mode and the cursor will turn intocrosshairs.

Click on the first point of the line to be measured and drag to theend point. The measurement will be given in blue text in the statusbar at the bottom of the screen.

The measuring unit is micron. To measure another line simply click on the measurement button

again.Annotating the Image

To display a label, micron marker, accelerating voltage, ormagnification on the image, select “Annotate Image” from the “Edit”pull-down menu. The mag., kV, and label should reflect currentparameters. By checking on and off appropriate boxes and clickingon the “Paste” button the chosen information will appear along thebottom of the image or map. Selecting a font size, font type, and color (black, white, white

on black, or black on white) are helpful features that emphasizethe text annotation.

Activating the spot mode or crosshair allows you to position thetext anywhere you would like before pasting it onto the image.

To display a line and measurement:1. Open the “Annotate Image” dialog box open and click on the

measurement button.2. Draw the line to be measured as instructed above. The length

will be displayed in the label section of the Annotate Imagedialog box.

3. Check the line check box and click on “Paste”.4. Check off the line check box and check on the label check box.5. Turn on the spot mode (cross hair) and position the red cross-

hair where the measurement text should appear.6. Click on “Paste”. Use the “Undo” button to undo the last

step.Any annotations will not be saved to the image unless the image issaved again.

PrintingIn most instances, the spectrum will have been collected in spotmode and the red crosshair should still be shown on the image in thecorrect location.

“File: Page Setup” Ensure that both the image and spectrum checkboxes have an "x" in them and the other parameters are as you wantthem to appear. Click on OK.

To print the spectrum and image choose Print while in the Spectrumview.

To print maps, select the maps while holding down the Ctrl key. Thedifferent views will print the maps in different sizes, fitting 1, 4or 16 maps to an 8”x11” page. Then select “File: Print” or click onthe printer button.

To print the spectrum, image, and quantification results on a singlepage, have the quantification data showing (by clicking on the “Q”button), then click on the printer button or select “Print” from the“File” pull-down menu.


(1) After this menu item has been selected, the cursor changesto an I-beam.

(2) Click on the spectrum at the point where the text is to beinserted. An edit box appears and the comment is typeddirectly into the box. The text will scroll if not all textcan be displayed in the edit box.

(3) Once all text has been entered, press Enter to insert thetext into the spectrum. Up to 32 characters can be enteredfor each text item and up to 10 comments can be added to aspectrum.

A comment can be changed or deleted from the spectrum by choosingthe Select Text menu item, then clicking on the existing commentin the spectral window. The text will be displayed in the editbox and can then be changed. To completely delete the comment,delete all text in the box and press Enter.

Peak ID You should select the Peak ID control panel by clicking on the

correct button (the left-most button out of the right-most group;the one that shows a spectrum with a “?”). You can then click on “Auto” for an auto-peak ID (the same can be

done by clicking on the “ID” button on the button bar). You mayneed to modify some of peaks identified. To remove an element,select the element from the “Saved Elem” list box and click the“Delete” button.

To add an element manually:(1) Type the four characters in “Element” box (e.g. SiKa,

AgLa, or K Ka, etc.).(2) Pick an element that is near the element you want to

add from the “Saved Elem” list and click “Z-” or “Z+”until the element of interest appears in the “Element”box, then click “Add”.

(3) Click the cursor on the peak that you want to identifyin the spectrum, then click on the choice from “PosElem” box and click “Add”.

After performing the peak identification procedure, there arecommonly some vertical lines on the spectrum that indicate theposition of the last peak or element requested during the peak IDstep. If the spectrum is to be printed, these lines will sometimesprint with the spectrum (in older versions of the software) and thisis rarely the desired result. To remove the line(s), first selectthe “Peak ID” control panel, then click on “View” and “ElementMarker”. A new method to remove these markers is to do a right orleft mouse click in the spectrum area.

HPD This button (found in the Peak Identification panel) is used to

calculate and display the background and deconvolution withoutdisplaying any quantification results. The user need not go to theQuantification Control Panel to calculate the background anddeconvolution. The HPD (in light blue) relies on the element listand correct kV when modeling.

HPD is used for confirming the present element list. A user canclick on the HPD button to see what the spectrum should look likewith the elements identified. If the HPD does not match thespectrum then adjustments can be made to the element list and theHPD button clicked again. These steps can be repeated until the HPD


matches the spectrum and all elements have confidently beenidentified.

In the instance when two peaks overlap the HPD is most useful. Acommon example of this is the overlap of the Sulfur K series peaksand the Molybdenum L series or the Titanium L peaks and the NitrogenK peak.

A spectrum, “Stnlss.spc”, provided in the D:Edax32:EDS:userdirectory has overlapping peaks of Fe, Cr, and Mn. Using the HPDwith only Fe and Cr identified will show a mismatch where Mn shouldbe. Adding Mn to the list and clicking on the HPD button then givesa good deconvolution model.

Standardless Quantification Before quantitative results can be reasonably accurate, the

collection parameters must be correctly specified (oxides orelements, etc.) and the analysis should satisfy three fundamentalassumptions of ZAF (Z - atomic number, A - absorption, and F -fluorescence) corrections:

(1) the sample should be smooth and flat(2) the sample (as seen by the beam electrons) should be

homogeneous(3) the sample should be infinitely thick to the

electron beam. If the sample is not smooth, then the geometry will be wrong and the

take-off angle incorrect. If the sample contains different phaseswithin the field of view examined, then the absorption correctionswill not be correct. If the sample contains a thin film or films,then the results will differ according to the voltage selected withdifferent penetration levels and a different proportion of substrateto the film will be sampled.

If the assumptions are reasonably well satisfied, then thequantitative result (even in standardless mode) will be reasonablyaccurate. (To test the degree of accuracy, standards can and shouldbe used that match the types of samples you will analyze. Analyzingthe standard as an unknown in standardless mode will provide datathat you can compare to its published values.)

To quantify a spectrum select the quantify control panel using thebutton that looks like a balance weighing out “Fe” and “Cr”,followed by the “Quantify” button, or by clicking one of the middlebuttons (the one between “ID” and “AUTO”) in the center of the mainbutton bar.

When the multiple results box is checked (in the Quant panel) newresults are appended to the previous quantification thus providingone print out or file with results from many spectra. **The resultsfrom the last spectrum quantified are displayed at the end of theresults.

Saving Quantification Data To save quantification results click on the “Save” button in the

Quantification panel, then follow standard Windows procedures forsaving a file. The results are saved as .CSV (comma separated values) files

which can be opened in any spread sheet program, typicallyMicrosoft Excel.

Printing To print the spectrum, first check the “Page Setup” dialog box found

under the “File” pull-down menu. There are several choices here forhow the spectrum and/or its quantitative results will appear.


Common choices are to select black and white (if using a LaserPrinter or if your color cartridge is bad) or to select thespectrum print out in outline mode --this will use less ink ofone specific color and will probably mean that the printout willphotocopy better.

Other options allow you to print overlain spectra andquantitative results.

When the multiple results box is checked in the “Page Setup”dialog box, the results from a series of spectra print organizedin order of element and parameter as opposed to in order ofsample.

The printing of the spectrum is accomplished by clicking on “File”and “Print” as is normally required in a Windows application.

Spectrum Overlay Under “View” on the menu bar you will find several choices on the

pull-down menu. The procedure used most often is the overlaying ofone spectrum on another for purposes of comparison.

To overlay a spectrum onto another one, click on “View”,“Compare...”, then check the “Overlay” box and then “Open” aspectrum from disk to be used as memory B for the overlay. (Thisrequires that you save the spectrum first before it can be used forthe overlay.) When the spectra are being shown in overlay mode,clicking the overlay off and back on again with the overlay buttonon the button bar (the one to the right of the Home/House button)becomes available.

CalibrationSelect the calibration control panel by clicking on the button fromthe right-most group that shows a spectrum with a caliper measuringa peak (third from the right usually). By default, this controlpanel assumes that you have aluminum and copper in the field ofview. Typical SEM parameters are 25 kV and a spot size to assure a30-35% deadtime for a given time constant, and a field of view withapproximately 7/8 of it occupied by copper (1/8 being aluminum).This should give a spectrum with the Al Ka peak (1.486 keV) and theCu Ka peak (8.04 keV) about the same height. If they are not equalthen you should move the stage slightly until the peaks are aboutequal. Typically, the maximum number of counts collected should beat least 5000. Clicking on “Start” will begin the calibrationprocedure. The time constant or pulse processing time can bechanged in the EDAM control panel and the calibration procedure willneed to be run for each time constant.

EDAX Training Course - X-Ray Count Optimization - page 2

.

EDAX Quiz on Peak ID - page 2

Decon02.spc. Between 0.5 and 15 keV, the peaks are:RhL, PdL, AgL.

SpecUtil Printouts of the K-, L- and M-Series Spectra

There are 10 spectra for the K-series peaks, 10 for the L, and 7 for the M-series peaks. Thepeak of interest is the largest peak in all cases or the peak with a dot over the peak. You willnotice that KS08 and LS02 are both the same spectra (Fe).

K-Series Spectra. At energies below about 2.5 keV, the alpha and beta peaks are notresolved or not present. The distance between the two peaks becomes greater at higheratomic numbers.

L-Series Spectra. At energies greater than about 3 keV, the L-series peaks consists of 6(or 7) peaks depending on the peak position and peak intensity: Ll, (Ln), La, Lb1, Lb2, Lg1,and Lg2 (from lower to higher energy). At energies below 3 keV there are typically only twopeaks that are resolved: the Ll and the La (the other peaks may be present but not resolved,and may make the La appear asymmetric). At low energies (below 1 keV), the Ll becomeslarger, and at very low energies (below about 0.6 keV) the Ll becomes larger than the La.

M-Series Spectra. At first glance, the M-series spectra are similar to the L-series spectra. Atenergies below 3 keV, there are only two significant peaks visible: the Mz and the Ma. Itmight be possible to also see a Mg and a M2N4 peak but these are very small. At lowenergies the Mz becomes larger and becomes the dominant peak at very low energies.Above an energy of about 3.0 keV, it becomes possible to resolve additional peaks, but atthis point we are at the highest atomic number portion of the periodic chart. There are no Mapeaks above 4 keV, and between 3 and 4 keV the only Ma peaks are for radioactiveelements such as Th, Pu and U.

Number K-Series L-Series M-Series

01 Be Ti02 C Fe W03 Al Ni Re04 Si Zn Os05 Sc Ru Pt06 V Pd Au07 Cr Ag Bi08 Fe Sn Th09 Ni Sb10 Zn Te

Peak ID Quiz -- page 2

PkID11.spc (easy). Between 1 and 10 keV, the peaks are:

PkID12.spc (easy). Between 1 and 10 keV, the peaks are:

Decon01.spc (very hard, maybe impossible). Between 1 and 10 keV, the peaks are (ormight be):

Decon01b.spc (very hard, maybe impossible). Between 1 and 10 keV, the peaks are (ormight be):

Decon02.spc (moderate to hard). Between 0.5 and 15 keV, the peaks are:


Characteristics of the K - Series Peaks

K-series peaks are typically fairly simple and consist of a Ka and a Kb peak. The Kb peakoccurs at a higher energy and starts to become resolvable from the Ka for atomic numbersgreater than sulfur (Z = 16). The Kb peak is usually 1/8 to 1/6 the size of the Ka peak as canbe seen in the spectrum below for titanium.

Characteristics of the L - Series Peaks

The L-series peaks are much more complex than the K-series peak(s), and may consist ofas many as 6 peaks: an La, Lb1, Lb2, Lg1, Lg2 and Ll. The peaks were arranged (in thelatter sentence) from highest energy to lowest energy with the exception of the Ll peak whichoccurs before (to the left of, or at a lower energy than) the La peak (see spectrum for tin onthe following page). Aside from the Ll peak which is a very small peak, the peaks areprogressively smaller with energy. For L-series peaks from elements less than the atomicnumber of silver (Z=47), this peak series is not resolvable. One of the common mistakes inpeak identification is to be unaware of the Ll peak and to hypothesize the existence of aminor or trace amount of an element that does not exist in the sample.


Characteristics of the M - Series Peaks

Most M-series peaks will show only two resolvable peaks, the Ma peak which also includesthe Mb (not resolved) and the Mz peak. Just as with the Ll line in the L-series peaks, the Mzoccurs at a lower energy than the Ma peak and there have been many instances ofidentifying another element by the analyst who did not recognize the Mz peak, or who wasusing a peak identification method that did not include the Mz peaks. For instance (seefollowing page), the Mz for osmium is perfect for being a small amount of Al or Br. The Mzfor gold is a good fit for the hafnium Ma peak, etc. M series peaks tend to be markedlyasymmetric due to the mixing together of the Ma and Mb (the Mb being a smaller peak at ahigher energy). To perform a manual peak ID for the M series peak, it is often necessary toclick the mouse cursor slightly to the left of the peak “centroid” because of this. When thepeak for the Ma is selected, the lines for both the Ma and Mb are shown. There may also bean Mg peak which may show up as low, high-energy shoulder for the large M peak, and avery small “M2N4” peak (see spectrum on the following page)

Auto Peak ID

Auto peak ID is fast, easy and will be reasonably accurate with K-series peaks that do nothave serious overlaps. Such an overlap would consist of a Ka from a trace element thathappens to be near a major peaks Kb (i.e. a trace of Mn with Cr, or V with Ti, etc.). Whenthe overlap consists of M, L and K series peaks, the auto peak ID routine is not well suited to


get all the elements correctly. In this case, the use of the peak deconvolution software isrecommended (see following discussion).

The auto peak ID routine makes use of an “omit” list, which is a list of elements that the autopeak ID will not find (see figure below). This list can be reached from the Peak ID controlpanel by clicking on “EPIC” (Edax Peak Identification Chart), the “Auto ID”. It is possible toremove elements from this list or to add elements. Manual ID will still list an element that isin this omit list.


Deconvolution and Peak ID

Deconvolution is used in the quantification routine to estimate the size and position of allpeaks associated with each assigned element. The fit of all the peaks calculated is shownas a lined spectrum on top of the background, so that any serious gaps or misfits can beobserved by the user. The deconvolved spectrum can be observed by clicking on the“Quant” button in the button bar and “OK” to remove the quantitative results from the display.It may be a good idea that your “results” mode should not be in “Multiple” mode for thisaction, since this may require several iterations and the intermediate results are seldom ofinterest.

If the spectrum has more counts as a cluster than the deconvolved spectrum, then themanual peak ID can be used to find a peak that can account for those peaks. In the casebelow, there are some counts that are not accounted for by the deconvolution in the area ofthe Cr Kb. This is common in a stainless steel and indicates the presence of the Mn Kapeak. It is also possible to subtract the deconvolution from the spectrum (click on “Proc” and“Subtract deconvolution”). This will make it more clear where a peak’s centroid should be.To undo the subtraction, click on “Edit” and “Undo”.

The peak-fitting routine used is most accurate for the K-series peaks. The complexity of theL-series peaks does not permit as accurate of a fit, but in most cases this fit will be morethan adequate to identify the peaks.


“overvoltage”. Typically, it is thought that the overvoltage should be two or greater forEDS analysis.

X-Ray Absorption

A consideration of the depth of excitation for low-energy x rays would lead us to believethat the low energy x rays may be produced nearly within the entire depth of penetrationof the electron beam. In actuality, even though this may be true for very low energy xrays, these x rays are also very easily absorbed by the sample and relatively few ofthem may actually escape from the sample except for those that were actuallygenerated near the sample surface. The loss of these absorbed electrons must becorrected for in the quantitative analysis. The ratio of absorbed to emitted x raysincreases with the accelerating voltage. As a result, absorption considerations alsoplaces an upper limit on our overvoltage --no more than 20 for qualitative work andideally less than 10 for quantitative analysis.

X-Ray Fluorescence

Characteristic x rays can be produced by other x rays as well as by high energyelectrons. This is typically referred to as x-ray-induced fluorescence or x-rayfluorescence. For instance, nickel K-alpha x rays have an energy near the criticalionization energy of iron K-alpha and will readily fluoresce iron x rays. This leads to anincrease in the iron peak in the spectrum and a decrease in the nickel peak beyondwhat would be expected given the abundance of the these two elements. Thefluorescence correction would correct for this effect by effectively removing some of theiron x-ray counts and placing them with the nickel x-ray counts.

Detector Efficiency

The efficiency of the EDS detector is controlled by the window type (if any), the goldcontact layer and the silicon dead layer. The super-ultra thin windows (SUTW) willtypically permit the detection of beryllium and boron, but not as efficiently as higheratomic number elements. The beryllium window is relatively good for K-radiation ofelements with atomic number greater than silicon (Z=14) but drops to what is basicallyzero for elements less than sodium (Z=11) in atomic number. Although not much of anissue in the SEM, there can also be inefficient detection for very high energy x raysbecause these x rays may pass through the entire detector thickness and create nodetectable signal.

X-Ray Artifacts

Peak Broadening. The resolution of the EDX detector is typically specified as theFWHM at manganese (Z = 25) and is on the order of 140 eV. There is a predictablerelationship that peaks of a lower atomic number will have a lesser FWHM (full width atthe half maximum height of a peak) than peaks at higher atomic numbers. When wecalibrate the spectrometer, the Al Kα and Cu Kα are used but the resolution at Mn Kα iscalculated or interpolated. The Al peak will typically have a much smaller FWHM thanthe Cu peak.


Peak Distortion / Asymmetry. Peaks in the spectrum will typically show an asymmetry inwhich the peak is usually sharper at the high end and this is partly due to the absorptionedge of the element. The tailing on the low-energy side of the peak is due in part toincomplete charge collection (not all electron-hole pairs are collected –this is thought tobe a problem for x rays that strike the detector near its edges).

Escape Peaks. Occasionally an x ray striking the detector will cause the fluorescence ofa silicon x ray. This may result in two x rays, one with the energy of silicon (1.74 keV)and one with the original x-ray energy minus the silicon energy. If both x rays remain inthe detector, the two x rays are summed and the correct energy assigned in the multi-channel analyzer. If the silicon x ray escapes from the detector, then what remains inthe detector is called an escape peak which has an energy that is 1.74 keV less than theoriginal x ray. Only x rays with energies greater than the absorption edge of silicon(1.84 keV) can cause the fluorescence of silicon, so we can expect to see the escapepeaks associated with K radiation for phosphorus and up in atomic number. The size ofthe escape peak relative to its parent peak (typically no more than a percent or two)actually diminishes at higher atomic numbers as a result of the higher energy x rays


tend to deposit their energy deeper in the detector where the silicon x rays (if generated)have more difficulty escaping from the detector.

Absorption Edges. The background of our spectrum will typically show a drop or anedge at the energy associated with the absorption edge of silicon and may showanother near the absorption edge of the gold M line. These result from the passagethrough the gold layer and silicon dead layer with a concomitant absorption of the x-raycontinuum.

Silicon Internal Fluorescence Peak. It is possible that the silicon dead layer of ourdetector may also be fluoresced by an incoming x ray and the resultant silicon x ray maythen travel towards the detector and produce a very small, but recognizable peak. It hasbeen estimated that this peak can be as high as 0.2 weight percent of some samples.This is difficult to verify or confirm, because just having the background correction notquite correctly specified, could easily produce a silicon content this high. Also, given thepoor quality of such a small peak, it could be easily confused with the silicon absorptionedge.

Sum Peaks. The sampling interval during which x rays are detected is a few tensnanoseconds. It is possible that two x rays of the same energy will enter the detectorwithin this time period and be counted as a single x ray of twice the energy.Compounds can give rise to sum peaks that are the sum of two different elementalenergies. Aluminum alloys will commonly have sum peaks (2.98 keV) that are equal tothe position of other elements, such as argon or silver. Sum peaks are typicallyproblems at higher count rates and when a phase is dominated by a single element. Todetermine if a small peak may be a sum peak (i.e. a detection artifact, notrepresentative of the composition of the sample), you can select sum peaks from thePeak ID control panel and it will show a marker for the most probable sum peak. Toconfirm that the peak in question is really a sum peak, save the peak and use this peakas an overlay. Then, lower the count rate (perhaps to ¼ of what it was) and collect anew spectrum. If the major peak is of a comparable size in both spectra and the signal-to-noise appears similar in both cases, but the peak in question is no longer visible orgreatly diminished, then the peak in the first spectrum was a sum peak. If the peak isundiminished, then it represents a real part of the sample.

Stray Radiation. Stray x rays are x rays that originate anywhere other than where theprimary beam interacts with the specimen and may be produced by a variety ofprocesses. Most occur as a result of x rays created by high-energy backscatteredelectrons striking the pole piece, stage, chamber or another part of the sample outsideof the imaged area. While it is possible for these x rays to enter the detector, carefulcollimation of the detector can eliminate most of this problem. Probably more seriousare backscattered electrons that strike the pole piece or stage and are exchanged foranother backscattered electron that returns to strike the sample at some distance fromthe point of interaction with the primary electron beam. It is expected that the amount ofstray radiation would be greatest when the sample is a rough surface or is near anedge. Backscattered electrons would be able to directly strike other surfaces of thesample and create x rays from these surfaces which may be well outside of the imagedarea. To minimize stray radiation, the sample should be smooth, and located at theworking distance that the detector is pointed at. It also helps to put the backscattered


electron detector in place because this acts as a sink for BSE and will protect the polepiece from being struck by BSE.

A Warming Detector. The current generation of EDAX detectors have a temperaturesensor which disables the detector when it runs out of liquid nitrogen. Just prior to thepoint when the detector will be disabled, you may notice an unusual, asymmetric “low-end noise peak”. At this time, the detector should have liquid nitrogen added to it. Thesystem can still be used for qualitative work provided that very low-energy peaks are notthe subject of the investigation. It should take approximately a half hour for the detectorto regain the ideal cooled condition. As mentioned, in the cooling period it can still beused for qualitative work, but the system should not be calibrated or used for any workwhere the very best resolution is required.


energy of the detected x-ray can be determined. The charge is collected to the terminalselectro-statically by a bias voltage applied across the detector. This voltage is 500 to1000 volts for most detectors. The transit time for the charge is ~50 nanoseconds.

Since the desired signal is made up of moving charge, any stray moving charges(currents) must be minimized. A semiconductor produces a thermally generated currentwhich must be reduced by lowering the temperature of the detector to eliminate thiscurrent as a noise compared to the signal. This involves cooling the detector with liquidnitrogen (77 degrees K). Si detectors need only to be cooled to ~90 degrees K, so somethermal losses can be tolerated. The Ge detector produces more current because of itssmaller band gap (which also causes the signal to be larger), so the cooling requirementis more critical. Cooling the detectors with mechanical devices is not usually done whenhigh image resolution is required because the vibration they produce cannot betolerated. Liquid nitrogen cooling is almost universally used for under these conditions.

In summary, the function of the detector is to convert x-ray energy into electrical charge.Later the processing of this signal will be discussed.

2. The detector efficiency.

Note in Figure 1 that the detector is made up of layers, some integral to the detector,and some external to it. An x-ray which strikes the detectors active area must beabsorbed by it in order for the charge signal to be created. The absorption of x-rays in alayer of thickness t is given by Beer's Law,

I I e

II

t/ ( )0

0

=

==

− µρ

µρ

Where := Final Intensity

Initial Intensity mass absorption coefficient

= densityt = thickness

With this equation the efficiency of the detector can be calculated, taking into accountthe absorbing layers in front of the detector (Be or Polymer window, Au metalization,and dead layer) as well as the thickness and material (Si or Ge)of the active region ofthe detector. Figure 2 shows a set of Si detector curves for a various detectorthicknesses and an 8 micron Be window. The 3 mm thickness would be most typical forcommercially available detectors.

The window material has the most dramatic effect on the low energy efficiency of eithertype of detector. Be windows have been used since the very first EDS detectors, butafter the early 1980's, ultra thin windows made of polymers have also becomeavailable, and in the last few years have become widely used. The Be window istypically between 7 and 12 microns in thickness, with the very thinnest available about 5microns thick. These only allow practical detection of the x-rays of Na (Z=11) and higheratomic numbered elements. The polymer type of super ultra thin windows (SUTW)


allow detection of possibly Be (Z=4), or certainly B (Z=5) and above. Table 1 shows acomparison of the efficiency of an ultra thin window to a Be window.

Table 1. Transmission of K x-rays through various windowsWindowType

B C N O F

8 micron Be 0% 0% 0% 0% 5%Ultra ThinPolymer

25% 85% 42% 60% 70%

If there are contamination layers present on either the window or detector, then the lowenergy efficiency will be adversely affected. These layers could be due to oilcontamination on the detector window or ice on the detector itself. (p. 14 of Ref 1) Allprecautions to prevent their formation should be taken. Each manufacturer will have aprocedure to remove them if they are formed.

3. The geometrical efficiency.

The collection of x-rays by the detector is affected by the solid angle that the detectorarea intercepts of the isotropically emitted x-rays from the sample. The largest possiblesolid angle is desirable, especially when small regions of the sample are beinginvestigated. The solid angle (Ω) in steradians is given by:

Ω =

=

A Where:A= detector area, mm

the sample to detector distance

/d

d

2

2

The area is most commonly 10 or 30 mm2 and the sample to detector distance variesfrom 10mm to 70mm, depending on the specific design of the microscope/detectorinterface. Solid angles of ~0.3 to 0.02 steradian are most common.

4. Signal Processing:

The charge from each x-ray event entering the detector must be processed and storedin a memory in order to make up a spectrum from an sample. The processing is outlinedbelow:

a. preamplifier:The preamplifier has the function of amplifying the charge signal and converting it to avoltage signal. A schematic is shown on the following page.


Reset

C

FET

Output

DetectorThe preamplifier.

The FET is mounted adjacent to the detector, and is cooled to ~ 120 degrees K toreduce its electrical noise. The configuration shown is called a charge sensitiveamplifier, and it converts charge at its input to a voltage output. C is a feedbackcapacitor. The FET must be reset periodically. This is accomplished by variousmethods, the most common being the pulsed optical feedback method.

v

Time ------>

Voltage(mv)

Output signal of an x-ray event

The output signal of an x-ray is shown above. The signal is small, and has noise formthe FET added to it. The voltage step v, contains the size of the x-ray event, and it mustbe processed further to amplify its size, and increase its signal to noise ratio.


b. The Signal processor.

The processor is usually an analog amplifier system. Digital signal processors are notyet in widespread use, so will not be considered here. The amplifier system has severalfunctions:

1. Amplify the signal to 0-10 volt range.2. Filter the signal to optimize the signal to noise ratio (optimize the energy resolution).3. Detect x-ray events that overlap or "pileup' on one another, creating erroneousinformation.

The filtering can be done with various kinds of networks, producing pulses that aregaussian shaped, triangularly shaped or trapezoidally shaped pulses. The networks canhave several different time constants available. The effect is to produce pulses that areabout 100 microseconds wide in order to achieve the best energy resolution. Thisincreases the probability of pulse pileup and the need to correct for it.

In order to detect the presence of pulse pileup, a second amplifier system is used just todetect x-ray events. This is often called an inspector channel. This inspector channelsenses when two events will pileup, and then rejects these events. The quality of thespectrum is maintained, but dead time is introduced, which increases at higher countrates.

For each time constant of the amplifier, a maximum throughput exists, which should notbe exceeded, but which can be approached. If a higher count rate is desired, then asmaller time constant can be used, which will have a higher throughput, but a poorerresolution.

Throughput curves for two time constants are shown below.


Thruput Curves

0

1000

2000

3000

4000

5000

6000

7000

8000

0 5000 10000 15000 20000 25000 30000

Input CPS

Stor

ed C

PS

50usec

100usec

c. The Multichannel analyzer.

The processed pulses are digitized using an Analog to Digital Converter. This devicemeasures the voltage height of each event and sorts the events into a multichannelmemory. This memory is organized such that each channel represents 10ev of energy.From this digitized spectrum, the x-ray intensities from each element can be obtained. Aspectrum is shown below.


5. Energy Resolution.

The resolution of the peaks observed generally follows the following relation:FWHM= SQRT[(FWHM) F E Where:F= f ano f actor= 0.11E= energ y of the x-ra y, e v= 3.8e v/charge pair (Si), 2.96e v/charge pair (Ge)

noise2 22 35+( . ) ]ε

ε

FWHM is the full width of the peak at half its maximum in ev. The noise term is due tothe electronic noise, primarily from the FET after signal processing has been applied. Itsvalue can vary from 40 eV to 100 eV, depending on the detector material, size, and ageof system. A typical detector may give resolutions as shown below. Older detectors mayshow poorer resolution below 2 KeV because of dead layer effects. Newer detectorsshow performance closer to the theoretical values due to improved manufacturingtechniques.

Resolution vs Energy for 70ev noise

0.00

50.00

100.00

150.00

200.00

250.00

0 5 10 15 20

Energy, Kev

FWH

M, e

v

FWHM

6. Collimation:

The detector must be shielded from x-rays produced from locations at other than thesample. X-rays are being produced wherever scattered electrons are striking portions ofthe column. The electron microscope itself must be designed to minimize such x-raysfrom reaching the detector through the sides of the detector. Also a collimator isdesigned to prevent the detector from "seeing" materials around the sample which maybe exposed to scattered electrons or x-rays from apertures in the column. In specialcases in the transmission electron microscope, a specially designed low backgroundsample holder is used which uses Be or another low atomic number alloy.


References:

1. X-Ray Spectrometry in Electron Beam Instruments ( D. Williams, J. Goldstein, and D.Newbury, eds.) Plenum Press, New York (1995)

2. Principles of Analytical Electron Microscopy ( D. C. Joy, A. Romig, Jr., and J.Goldstein, eds. ) Plenum Press, New York (1989)

EDAX Phoenix Training Course - X-ray Signal Generation - page 1

X-RAY SIGNAL GENERATION

Signal Origin

The interaction of the electron beam with specimen produces a variety of signals, butthe most useful to electron microscopists are these: secondary electrons (SE),backscattered electrons (BSE) and x rays. The SE signal is the most commonly usedimaging mode and derives its contrast primarily from the topography of the sample. Forthe most part, areas facing the detector tend to be slightly brighter than the areas facingaway from the SE detector, and holes or depressions tend to be very dark while edgesand highly tilted surfaces are bright. These electrons are of a very low energy and veryeasily influenced by voltage fields.

The BSE signal is caused by the elastic collision of a primary beam electron with anucleus within the sample. Because these collisions are more likely when the nuclei arelarge (i.e. when the atomic number is large), the BSE signal is said to display atomicnumber contrast or “phase” contrast. Higher atomic number phases produce morebackscattering and are correspondingly brighter when viewed with the BSE detector.

X-ray signals are typically produced when a primary beam electron causes the ejectionof an inner shell electron from the sample. An outer shell electron takes its place butgives off an x ray whose energy can be related to its nuclear mass and the difference inenergies of the electron orbitals involved. The Kα x ray results from a K shell electronbeing ejected and an L shell electron moving into its position. A Kβ x ray occurs whenan M shell electron moves to the K shell. The Kβ will always have a slightly higherenergy than the Kα and is always much smaller. Similarly, an Lα x ray results from anM shell electron moving to the L shell to fill a vacancy (see Figure below). Theoccurrence of an Lβ x ray means that an N shell electron made the transition from the Nshell to the L shell. The Lβ is always smaller and at a slightly higher energy than the Lα.The L-shell x rays are always found at lower energies than the K lines. Because thestructure of the electron orbitals is considerably more complex than is shown below,there are actually many more L-shell x-ray lines that can be present (it is not uncommonto see as many as 5 or 6). M-shell x-ray peaks, if present will always be at lowerenergies than either the L or K series.


In energy-dispersive spectroscopy (EDS), the x rays are arranged in a spectrum by theirenergy and (most commonly) from low atomic number (low energy) to high atomicenergy (higher energy). Typically, the energies from 0 to 10 keV will be displayed andwill allow the user to view: the K-lines from Be (Z = 4) to Ga (Z = 31); L-lines Ca (Z =20) to Au (Z = 79), and M-lines from Nb (Z = 41) to the highest occurring atomicnumbers. From the interpretation of the x-ray signal, we derive qualitative andquantitative information about the chemical composition of the sample at themicroscopic scale.

Spatial Resolution

The spatial resolution of these signals are significantly different from each other. Thefigure below is a representation of the depth of penetration of the electron beam into asample. No scale has been placed on this image, but the depth of penetrationincreases as the accelerating voltage of the primary beam is increased. It will also bedeeper when the sample composition is of a lower density and/or is of a relatively lowaverage atomic number. All three of the signals discussed above are producedthroughout this interaction volume provided the beam electrons still have enough energyto generate it. However, some electrons or x rays may be of lesser energy andgenerated at a considerable depth in the sample. Thus, they may be absorbed and notgenerate a signal that can escape from the sample.

The SE signal is one that is readily absorbed and therefore we are only able to detectthe SE signal that originates relatively close to the surface (i.e. less than 10 nm). TheBSE signal is of higher energy and is able to escape from a more moderate depth withinthe sample as shown. The x-ray signal can escape from a greater depth, although thex-ray signal absorption is actually variable depending upon its energy. For example,oxygen is of relatively low energy and can only escape from the near-surface region ofthe sample, while iron is of significantly higher energy and would escape from a greaterdepth. In quantitative x-ray analysis, it is possible to compensate for these effects withthe absorption correction.


Although the discussion thus far has only mentioned the depths from which the signalcan emerge, the width of the signal is proportional to its depth and provides an estimateof the signal resolution. Because the SE signal that is generated at even relativelyshallow depths is absorbed, its resolution depends primarily on the position of theentering electron beam which has a spread related to the electron probe diameter or thespot size of the electron beam. The x-ray signal can emerge from greater depths(especially high-energy x rays) and the lateral spread of the primary beam electron canbe quite large relative to the beam diameter. The only effective way to improve theresolution of these signals is to decrease the accelerating voltage which will decreasethe beam penetration. The BSE signal is in between these two extremes and itsresolution can be improved by decreasing the spot size to some extent, but therelationship between spot size and resolution is not as direct for the BSE signal as forthe SE signal. The resolution of the BSE signal can also be improved by lowering theaccelerating voltage, although this usually means having to increase the gain of the BSEdetector and may result in a degradation of the signal-to-noise ratio of the image.

Directionality of Signals

All of the signals that emerge from the sample can be considered to be directional to atleast some extent. A directional signal can be recognized in a photomicrograph of asample that displays topography because there will be a very harsh contrast such thatsurfaces that face the detector will be bright and surfaces that face away from thedetector will be dark. If the trajectory of the signal can be altered to favor detection, or ifa symmetric array of detectors is employed, the effect of directionality is minimized.

The trajectories of the SE signal are influenced by a positive voltage on a wire meshnetwork in front of the detector which attracts the SE from the sample, even fromsurfaces that face away from the detector. The BSE detector is typically arranged in anarray such that they collect signals from a large, symmetrically arranged area. SomeBSE detectors consist of two or more segments and the appearance of illuminationdirection in the imaged area changes drastically depending on which detector orsegment is used for imaging. When all segments are selected, the result is a balanced,symmetric image that does not show an apparent directionality in its illumination.

The x-ray signal is effectively the most directional of all the signals because there is onlyone detector and it is usually at a 35 degree angle to the surface of the sample. Thereis certainly no simple way to influence the trajectory of x rays to increase the efficiency


of the detector. As a result, if one is trying to collect the x-ray signal from a surface thatslopes away from the detector, the x-ray count rate will be greatly diminished. If atopographic high area is between the imaged area and the x-ray path to the detector,there will also be few detected x rays. The effects of directionality for the x-ray signalare greatly diminished when working with polished samples rather than samples with alarge topographic variation.

The Analysis of Rough Surfaces or Particles

There are difficulties associated with trying to analyze samples with anything other thana smooth surface. The figure on the next page shows a cross-sectional configurationwith a detector at right and a small sample or portion of a sample at the left. Theinteraction volume is shown when the beam is at three different locations (‘A’, ‘B’ and‘C’) and the shaded region represents the area from which a low-energy signal mayescape from the sample without being absorbed. The arrows represent the flux of theselow-energy signals which will be highest at ‘A’ and at ‘C’ but relatively low at ‘B’.

If the low-energy signal is the secondary electron signal and the detector at the right isthe secondary electron detector (with a positive grid voltage), then the edges near ‘A’and ‘C’ will appear brighter than the center of the sample at ‘B’. Alternatively, if the low-energy signal is some relatively low energy x ray (such as aluminum in a nickel alloy, oroxygen in a mineral, or the copper ‘L’ x-ray signal as compared to the copper ‘K’ x rays),and the detector is the EDS detector, then the height of the low energy peak would behighest at ‘C’ and lowest at ‘A’. Note that even though there would be a high flux oflow-energy x rays leaving the sample at ‘A’, that these will not be detected becausethere is no detector positioned so as to intercept the signal.

Another difficulty in analyzing particles or rough surfaces is when the surface of theparticle has a slope which is not parallel to the surface of the stage. In the figure shownabove, the upper surface is shown parallel to the stage and our consideration was reallycentered on what might be regarded as “edge” effects. However, when the samplesurface is inclined toward the detector at a greater angle than the stage surface, thenthe take-off angle will be greater than that of a parallel surface. If our sample consistsof a single, non-parallel sloping surface, then its take-off angle could be determined andan accurate analysis performed, provided that we have some way of knowing the localsurface tilt of the sample. If the sample is rough and consists of many surfaces ofvariable orientation, then it is unlikely that a reliable analysis can be performed.


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EDAX Phoenix Training Course –Introductory Diagrams - page 1