Upload
others
View
4
Download
0
Embed Size (px)
Citation preview
© Oxford University Press 2013. All rights reserved.
Chapter 10
Nanometrology
1
Nanometrology is the science of measurement at the nanoscale level. Figure illustrates where nanoscale stands in relation to a meter and sub‐divisions of meter.
Nanometrology addresses two main issues; the precise measurement of sizes in the nanometre range, and adapting existing or developing new methods to characterize properties as a function of size.
Introduction
2
Type of nanomaterial
Material Diameter / thicknessin ‘nm’
Nanocrystals
Nanofilms
Nanowires
Nanotubes
Nanosurfaces
Metals, Inorganic materials (oxides, nitrides, sulphides, etc)
Layers of quantum dots made of lead selenide, indium arsenide, etc
Metals, oxides, nitrides, sulphides, etc
Carbon, metals, inorganic materials
Various materials
1‐50
1‐10
1‐100
1‐100
1‐1000
Types of Nanomaterials
3
Nanosensors
Water Purification
Lighting
Nanocomputers
Nano technology based clothes
Applications of Nanotechnology
4
Sl. No. Parameter / Property Measurement Technique1
2
3
Morphology: size and shape of particles, Crystallographic information: detection of atomic scale defects
Topography: the surface features, Morphology: shape and size of the particles, Composition: the elements and compounds the sample is composed of, Crystallographic
Three dimensional surface topology: size, shape, roughness, defects, electronic structures
Transmission Electron Microscopy (TEM)
Scanning Electron Microscopy (SEM)
Scanning Tunneling Microscopy (STM)
Nanometrology Techniques
5
Sl. No. Parameter / Property Measurement Technique
4
5
Topology, roughness and elasticity of surface, grain size, frictionalcharacteristics, specific molecularinteractions and magnetic featureson surface.
Crystallographic information: type of crystal structure, film thickness, interface roughness and surface topology.
Atomic Force Microscopy (AFM) or Scanning Force Microscopy (SFM)
X‐ Ray Diffraction (XRD)
Nanometrology Techniques
6
Transmission electron microscopy (TEM) is a microscopy technique in which a beam of electrons is transmitted through an ultra‐thin specimen, interacting with the specimen as it passes through.
An image is formed from the interaction of the electrons transmitted through the specimen; the image is magnified and focused onto an imaging device, such as a fluorescent screen, on a layer of photographic film, or to be detected by a sensor such as a CCD camera.
Transmission Electron Microscope
7
8
Transmission Electron Microscope
9
HRTEM: A faulted particle in a NiTiPt high‐temperature shape memory alloy
Transmission Electron Microscope
10
Transmission Electron Microscope
TiNi shape memory alloy
Source: http://martens.pse.tut.ac.jp/tsuchiya/TiNifoil.html
The scanning electron microscope is arguably the most versatile microscope with magnification ranging from 5X to as high as 106X. It provides excellent resolution, compliant to automation and user friendly.
These features have made it the most widely used of all electron beam instruments. The sample preparation and examination is also relatively simple compared other techniques.
A wide range of nanomaterials, starting from powders to films, pellets, wafers, carbon nanotubes, and even wet samples can be examined. It is also possible to correlate the observations made at nan scale to macro scale and draw reliable conclusions.
Scanning Electron Microscope
11
Scanning Electron Microscope
12
A scanning electron microscope (SEM) is a type of electron microscopethat produces images of a sample by scanning it with a focused beam of electrons.
The electrons interact with atoms in the sample, producing varioussignals that can be detected and that contain information about thesample's surface topography and composition.
SEM can achieve resolution better than 1 nanometer.
Specimens can be observed in high vacuum, in low vacuum, in wetconditions (in environmental SEM), and at a wide range ofcryogenic or elevated temperatures.
1313
Scanning Electron Microscope
Scanning Electron Microscope
14
Sample preparation All samples must be of an appropriate size to fit in the specimen
chamber and are generally mounted rigidly on a specimen holder calleda specimen stub. Several models of SEM can examine any part of a 6‐inch (15 cm) semiconductor wafer, and some can tilt an object of thatsize to 45°.
For conventional imaging in the SEM, specimens must be electricallyconductive, at least at the surface, and electrically grounded to preventthe accumulation of electrostatic charge at the surface.
Metal objects require little special preparation for SEM except forcleaning and mounting on a specimen stub.
Nonconductive specimens: They are usually coated with an ultrathincoating of electrically conducting material, deposited on the sampleeither by low‐vacuum sputter coating or by high‐vacuum evaporation.Conductive materials in current use for specimen coating include gold,gold/palladium alloy, and graphite.
15
SEM images
Scanning Electron Microscope
Scanning electron microscope photograph of a textured silicon surface. University of New South Wales.
SEM of polymer fibers.
16JEOL JSM‐7001F Scanning Electron Microscope
Scanning Electron Microscope
17
Student Presentations
A scanning tunneling microscope (STM) is an instrument for imaging surfaces at the atomic level. Its development in 1981 earned its inventors, Gerd Binnig and Heinrich Rohrer (at IBM Zürich), the Nobel Prize in Physics in 1986.
The STM works on the principle of quantum tunneling. When an atomically sharpened tip under a small voltage is brought close to the surface of a sample, so that the separation is of the order of a nanometer, there is a small change in current in the circuit. This effect is called the quantum tunneling effect.
The induced current is referred to as the tunneling current. The tunneling current increases as the gap between the tip and the sample decreases.
The change in tunneling current can be calibrated with respect to the change in gap In other words if we scan the tip over the sample
Scanning Tunneling Microscope
18
Components of STM
Scanning Tunneling Microscope
19
An AFM is rather different from other microscopes, because it does not form an image by focusing light or electrons onto a surface, like an optical or electron microscope.
An AFM physically ‘feels’ the sample’s surface with a sharp probe, building up a map of the height of the sample’s surface.
By scanning a probe over the sample surface it builds up a map of the height or topography of the surface as it goes along.
Atomic Force Microscope
20
Laser Deflection contact AFM
Atomic Force Microscope
21
X-ra Diffraction System (XRD)
X‐ray diffraction is an ideal method for examining samples of metals, polymers, ceramics, semiconductors, thin films and coatings.
It can also be employed for forensic and archeological analysis.
A two‐dimensional diffraction pattern provides abundant information about the atomic arrangement, microstructure, and defects of a solid or liquid material.
X Ray Diffraction System (XRD)
22
Bragg’s Law
Bragg law describes the relationship between the diffraction pattern and the material structure. If the incident X‐rays hit the crystal planes with an incident angle θ and reflection angle θ as shown in figure in the next slide, the diffraction peak is observed when the Bragg condition is satisfied
That is, nλ = 2d.sin θ
where λ is the wavelength, d is the distance between each adjacent crystal planes, θ is the Bragg angle at which one observes a diffraction peak, and n is an integer number, called the order of reflection.
X Ray Diffraction System (XRD)
23
Bragg Law
X Ray Diffraction System (XRD)
24
2D X Ray Diffraction System (XRD)
25