Upload
duongcong
View
217
Download
0
Embed Size (px)
Citation preview
Complementary Techniques:Co p e e ta y ec ques:An Introduction to XPS, AES and
ToF-SIMS for Surface Analysis
John F WattsThe Surface Analysis Laboratory
Surrey Materials Institute & School of Engineering
Ion Beam Centre Training Course for Young Researchers
26 – 30 March 2007
Analytical Techniquesy q
Surface AnalysisSurface Analysis
The Principal MethodsThe Principal Methods
• X-Ray Photoelectron Spectroscopy
XPS• XPS
• Auger Electron Spectroscopyg p py
• AES/SAM
S d I M S• Secondary Ion Mass Spectrometry
• SIMS
XPS ChecklistXPS Checklist
• Depth of analysis 5nm
• All elements except hydrogen• All elements except hydrogen
• Readily quantified
• All materials (vacuum compatible)
• Depth profiling by ARXPS or sputtering
• Analysis area mm2 to 10 micrometres
XPS BasicsXPS - Basics
C1s
N1sO1s
EB = hν - EK - ω
XPS – Relationship to XPS – Relationship to Electronic Structure
XPS Survey SpectrumXPS Survey Spectrum
5
5
5
survey O1s
Ge2pGeLMM
Note:
C1s spectrum
5
5
OKLL
p p
XPS and Auger peaks
5
5 OKLLCKLL
peaks
Background –stepwise
5
5
Ge3dC1s stepwise
Valence band0
01002003004005006007008009001000110012001300
Binding Energy (eV)
Chemical shift
XPS SpectrometersXPS Spectrometers
Depth of AnalysisDepth of Analysis
XPS Survey SpectrumXPS Survey Spectrum
5
5
5
survey O1s
Ge2pGeLMM
Note:
C1s spectrum
5
5
OKLL
p p
XPS and Auger peaks
5
5 OKLLCKLL
peaks
Background –stepwise
5
5
Ge3dC1s stepwise
Valence band0
01002003004005006007008009001000110012001300
Binding Energy (eV)
Chemical shift
Germanium XPS and X-AESGermanium XPS and X AES
Ge3d Ge(0)GeLMMGe(IV) Ge3dGeLMM
Ge(IV)
Ge(0)
Ge(IV)
Ge(IV)Ge(0)
8.0 eV
Ge(0)
4 0 V
Ge(IV)
8.2 eV4 0 V
30
Binding Energy (eV)
4.0 eV
1140 1150 1160 1170 1180
Kinetic Energy (eV)
1220
Binding Energy (eV)
4.0 eV
Ge3d: EK = 1453 eV
λ = 2.8 nm
GeLMM: EK = 1140 -1180 eVGe2p: EK = 264eV
λ =0.8 nm
Valence Band SpectraValence Band Spectra
Polyolefines such as poly(ethylene) and Polyolefines such as poly(ethylene) and poly(propylene) have identical C1s spectra but
very characteristic valence bandsvery characteristic valence bands
Failure AnalysisFailure Analysis
Canned beer is id d i h d provided with a dense
head by carbon dioxide contained in plastic “widget”plastic widget
Polymer to Metal InterfacePolymer-to-Metal Interface
C1s
O1s400 μm XPS
Epoxy Lacquer Epoxy Lacquer
μ
2 mm
N1s
2 mm
Nylon Nylon
C1s Spectrum of EpoxyC1s Spectrum of EpoxyCH3 OH CH3
2HC
O
CH CH2 O C
CH3
O CH2 CH CH2 O C
CH3
O CH2 CH
O
CH2
n
Carom.Caliph.
C OC O C-Oarom.C-Oaliph.
CCepoxy
XPS Information DepthXPS Information Depth
“Surface Angle”
Depends Upon Take-Off Angle
“Bulk Angle” g
Minor Additive in Organic CoatingMinor Additive in Organic Coating
Elemental depth profile concentration of CC+FA1
90
100 The addition of poly(acrylic)
60
70
80
atio
n (A
t. %
)
Carbon
of poly(acrylic) flow agent in the formulation
30
40
50
omic
con
cent
ra
Oxygen
Nitrogen
induces a displacement
f th
0
10
20Ato of the urea
component deeperin the coating
0 1 2 3 4 5 6Depth (nm)
in the coating
Boeing Wedge Test Failure SurfacesBoeing Wedge Test Failure Surfaces
Epoxy Adhesive + 1% GPS: XPS Images
Opticalmirror images
C1s Al2p Si2p
Epoxy Adhesive + 1% GPS: XPS Images
mirror images
XPS SpectrometersXPS SpectrometersAxis Ultra
A l i lKratos Analytical
K-Alpha
Quantum 2000Physical Electronics
K AlphaThermo
ESCALAB 250Thermo
Theta ProbeThermo
AES ChecklistAES Checklist
• Smallest volume of any analytical techniquey y q• 10 nm ultimate spatial resolution• Metals and semiconductors• Chemical information (CCC transitions)• Quantification (not as easy as XPS)y• Depth profiling with sputtering
AES ChecklistAES ChecklistImportant considerations
S i l l iSpatial resolutionSEMSAMSmall feature analysis (at low beam
energy)SensitivitySensitivity
Minimise acquisition timMaximise signal to noise ratio
Spectral ResolutionResolve interferencesChemical state analysisMap dopants
Depth ProfilesDepth ProfilesDepth resolution
Auger Electron SpectroscopyAuger Electron Spectroscopy
EKL2,3L2,3(Z) = EK(Z) – [EL2,3(Z) + EL2,3(Z + 1)]
AES/SAM System GeometryAES/SAM System Geometry
Field EmissionElectron Source
Electron Optical
Ion Gun Energy Analyser
Column
LensSpecimen
Scanning Auger MicroscopeScanning Auger Microscope
Auger Microprobe for chemical imaging g p g gSpatial Resolution
<7 nm (SEM)<12 (SAM)<12 nm (SAM)
High Energy ResolutionExcellent Performance even at Excellent Performance even at low beam energyDepth Profiling with precision and sensitivityMultitechnique capability
i h i l XPS EDX with optional XPS, EDX or backscattered electron detector
AES Spectral ResolutionAES Spectral Resolution
AlKLL Auger spectra from thin Al2O3 layer on Al
Scanning Auger Microscopy: Scanning Auger Microscopy: Resolution
Depth ProfilingDepth Profiling
U f i t d th Use of an ion gun to erode the sample surface and re-analyse
E bl l d b Enables layered structures to be investigated
I i i f i fInvestigations of interfaces
Depth resolution improved by:
Low beam energies
Small ion beam sizesSmall ion beam sizes
Sample rotation
Depth ProfilingDepth Profiling
Superb Depth Resolution from metal multilayer structure (layer thickness only 5nm), achieved by:–Low ion beam energy–Azimuthal rotation of specimen during sputtering cyclep g p g y–Almost grazing incidence analysis by use of specimen tilt
AES Chemical State Depth ProfileAES Chemical State Depth Profile
AES Ball CrateringAES Ball Cratering
Depth of crater, d, relative to diameter of crater and radius of ball is given by:o ba s g e by:
d = D2/8R
If x is the radial distance from If x is the radial distance from the edge of the crater to the revealed buried layer then the d th f th l b depth of the layer, z, can be shown to be:
( )x
Taper Sectioning
( )xDRxz −=
2Taper Sectioning
Ball Cratering MachineBall Cratering Machine
S h i di f b ll Schematic diagram of ball cratering machine. Ball is usually ca 30 mm diameter usually ca. 30 mm diameter, fine diamond paste is abrasive.
Once crater is eroded sample is Once crater is eroded sample is lightly sputtered in Auger system prior to analysis to system prior to analysis to remove carbonaceous contamination. AES is carried out along crater walls which is then converted to a compositional depth profilecompositional depth profile.
Depth Profile Zn Coated SteelDepth Profile Zn Coated Steel
D h fil f 30 i f i l Depth profile of a 30 mm coating of zinc on steel, treated with a chromate conversion coating.
Combined AES/EDXCombined AES/EDX
This option on a SAMThis option on a SAM enables bulk analyticalanalytical information (by EDX) to be obtainedEDX) to be obtained in exact register with the surface (AES)the surface (AES) data. Repositioning of the sample is notof the sample is not necessary
Grain Boundary EmbrittlementGrain Boundary Embrittlement
Failure of rotor of turbine at Hinkley Point ypower station during routine overspeed test.p
This is a classic example f th t t hi of the catastrophic
nature of intergranular f tfracture.
FractographyFractography
F il l Failure occurs along the prior Austenite
i b d i grain boundaries, complete absence of
l i d f i plastic deformation or other energy b bi absorbing process.
Brittle FailureBrittle Failure
In Situ Fracture StageIn Situ Fracture Stage
F th t d f For the study of grain boundary
ti segregation phenomena in
t l th l metals the sample must be fractured, i i t l in an intergranular manner, within the UHV f th A UHV of the Auger microscope
Hot Cracking of Steel WeldmentHot Cracking of Steel Weldment
AES S EDX CAES: S, EDX: Cr
Hot Cracking AES/EDXHot Cracking AES/EDX
EDX alone would indicate that the enhanced Cr lt f th t f C O i k AES was a result of the present of Cr2O3 in crack. AES
data alone would indicate that sulphur segregation is the cause of ductility-dip cracking.
AES d EDX t th i di t d C i h AES and EDX together indicates a second Cr-rich phase has formed at grain boundaries: Liquation Cracking
Chemical State in AESChemical State in AES
AES D h P fil i h Ch i l S l iAES Depth Profile with Chemical State resolution
AES/SAM of CeramicsAES/SAM of Ceramics
SWithout charge compensation
SEM
Red = NitrogenGreen = Oxygen
With charge compensation (Ar+ 20 eV)
SIMS ChecklistSIMS Checklist
• Surface mass spectrometry – static SIMS• Ultimate detection limit – ppb for B in Si• Ultimate detection limit – ppb for B in Si• Molecular specificity – polymers• Rapid acquisition• Rapid acquisition• Imaging• Quantification needs very similar standards• Quantification needs very similar standards• Depth profiling - DSIMS
The Sputtering ProcessThe Sputtering Process
Primary ion beam (Ar, Ga, Bin+, Cs, nC60) is used to sputter secondary ions and neutrals.
Secondary ions are Secondary ions are analysed in mass spectrometer
Argon ions impacting on copper surface© Roger Webb
spectrometer
© Roger Webb
ToF-SIMSToF-SIMS
ToF-SIMS Operational ModesToF SIMS Operational Modes
Surface Spectroscopy
Surface ImagingSurface Imaging
Depth Profiling
Modern ToF-SIMS SystemModern ToF SIMS System
Modern ToF-SIMS SystemModern ToF-SIMS System
Defect in Paint FilmDefect in Paint Film
Specific Interactions by ToF-SIMSSpecific Interactions by ToF-SIMS
The intense SiOAl+
peak
is indicative of a covalent
b b hbond between the
aluminium oxide and th the
organosilane
dh i adhesion promoter
C60 Depth Profile of PolymersC60 Depth Profile of Polymers
1.00E+05
F
nts
1.00E+04
Cou
n
O
C1.00E+03
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0
Time / s
Molecular IonsMolecular Ions
1.00E+05
C3HF4-
1.00E+04
Coun
ts
C4H5O+
C3H2F5-
C2H5O+
1.00E+030 1 2 3 4 5 6 7 8 9 10
Time / s
Low Angle Microtome SectionsLow Angle Microtome Sections
Microtome Knife
Sample
P l l Bl kPolypropylene Block
Angle ranges from 2.0 –0.03o by use of sectioning
blocks of different geometriesgeometries
ULAM GeometryULAM Geometry
Small area XPS analysis mode (100 μm)
XPS spot i /
ULAM taper angle/o
0.03 0.33 2.0size/μm 0.03 0.33 2.0
100 60 600 3500Coating
Substrateθ
15 13 100 500
Depth Resolution ULAM/nm
ToF-SIMS Images of ULAM InterfaceToF SIMS Images of ULAM Interface
b)a)
Polyurethane ions
(a) m/z = 149: C8H5O3+
d)c)
2
(b) m./z = 26: CN-
(c) m/z = 59: C3H4F+
(d) / 19 F
3
2 (d) m/z = 19: F-
1
PVdF ions
Negative SIMS Spectra from ImagesNegative SIMS Spectra from Images
35 00a)25
20 00
25 00
30 00
unts 66
Point 2: Bulk Polyurethane
c)
5 00
10 00
15 00
Cou
41-4249
100
121
)
2
00 20 40 6 0 80 10 0 1 20 14 0 160 1 80 20 0
m /z
1 2 0 0 0
1 3 5 0 0
1 5 0 0 0c) 191
3
6 0 0 0
7 5 0 0
9 0 0 0
1 0 5 0 0
Cou
nts
39
Point 1: Bulk PVdF
0
1 5 0 0
3 0 0 0
4 5 0 0
0 2 0 4 0 6 0 8 0 1 0 0 1 2 0 1 4 0 1 6 0 1 8 0 2 0 0
49
39
85
0 2 0 4 0 6 0 8 0 1 0 0 1 2 0 1 4 0 1 6 0 1 8 0 2 0 0m /z
Reconstructed ToF-SIMS of InterfaceReconstructed ToF SIMS of Interface
1 4 0 0b)19
Point 3: PU and PVdF at Interface
8 0 0
1 0 0 0
1 2 0 0
ount
s
85
Point 3: PU and PVdF at Interfacec)
2
2 0 0
4 0 0
6 0 0
C
31
55 71
87 121185141
3
00 20 4 0 6 0 8 0 1 0 0 12 0 1 4 0 1 60 1 8 0 20 0
m /z
1
ToF-SIMS of AdditiveS S dd
2400
2700
3000
31
1500
1800
2100
2400
ount
s
71
85
41
600
900
1200
Co
55 x10
0
300
30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200
m/z
185
A negative ion ToF-SIMS mass spectra of the pure acrylic co-resin component of the PVdF topcoat formulation in the mass range 30-200m/z.
ToF-SIMS of Acrylic Copolymer Component of PVdF Topcoat
Acrylic ImagesAcrylic Imagesa) b)
Negative Ion Mass
Selected Images
d)c)
g
(a) m/z = 31: CH3O-
(b) m/z = 55: C3H3O-(b) m/z 55: C3H3O
(c) m/z = 71: C3H3O2-
(d) m/z = 85: C H O -
e) f)
(d) m/z = 85: C4H5O2
(e) m/z = 87: C4H7O2-
(f) / 141 C H O -(f) m/z = 141: C9H13O4-
SummarySummary• All three have various hierarchies of use ranging All three have various hierarchies of use ranging
from simple elemental analysis to in-depth chemical characterisation at high spatial resolution
• XPS, AES and SIMS are powerful analytical methods for the chemical and elemental characterisation of surfacescharacterisation of surfaces
• For metallurgical studies AES/SAM is perhaps the most useful
• For polymers a combination of XPS and ToF-SIMS is hard to beat
• Surface analysis is expensive!