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Surface and Materials Analysis Techniques

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Title: Surface and Materials Analysis Techniques


1
Surface and Materials Analysis Techniques
  • Nanotechnology
  • Foothill DeAnza Colleges

2
Your Instructor
  • Robert Cormia
  • Associate Professor, Foothill College
  • Informatics and Nanotechnology
  • Background in surface chemistry and surface
    modification, materials analysis,
  • Contact info
  • rdcormia_at_earthlink.net ph. 650.747.1588

3
Overview
  • Why characterize?
  • Techniques
  • Approaches
  • Examples
  • Where to learn more

4
Why Characterize?
  • Nanostructures are unknown
  • QA/QC of fabrication process
  • Failure analysis of products
  • Materials characterization
  • Process development / optimization

5
Characterization Techniques
  • Surface analysis
  • Image analysis
  • Organic analysis
  • Structural analysis
  • Physical properties

6
Types of Approaches
  • Failure analysis
  • Problem solving
  • Materials characterization
  • Process development
  • QA/QC

7
Industry Examples
  • Semiconductors and MEMS
  • Bionanotechnology
  • Self Assembled Monolayers (SAMs)
  • Thin film coatings
  • Plasma deposited films

8
Surface Techniques
  • AES Auger Electron Spectroscopy
  • XPS X-ray Photoelectron Spectroscopy
  • SSIMS Static Secondary Ion Spectroscopy
  • TOF-SIMS Time-Of-Flight SIMS
  • LEEDS Low Energy Electron Diffraction

9
Surface Analysis
  • Electron Spectroscopies
  • XPS X-ray Photoelectron Spectroscopy
  • AES Auger Electron Spectroscopy
  • EELS Electron Energy Loss Spectroscopy
  • Ion Spectroscopies
  • SIMS Secondary Ion Mass Spectrometry
  • SNMS Sputtered Neutral Mass Spectrometry
  • ISS Ion Scattering Spectroscopy
  • RBS Rutherford Back Scattering

The Study of the Outer-Most Layers of Materials
(lt100A)
10
XPS/AES Analysis Volume
11
AES - Auger
  • Surface sensitivity
  • Microbeam
  • Depth profiling
  • Elemental composition
  • Some chemical bonding

12
Why the Odd Name?
13
Surface Sensitivity
  • Escape depth of electrons limits the sample
    information volume.
  • For AES and XPS, this is 40 Angstroms.
  • Angle of sample to detector can be varied to
    change the surface sensitivity.

14
Auger Data Formats
Raw Data
Differentiated Data
15
Auger Instrumentation
PHI Model 660 Scanning Auger Microprobe
16
Sputtering (Ion Etching) of Samples
17
Al/Pd/GaN Thin Film Example
(cross section)
18
Al/Pd/GaN Profile Data
19
Al/Pd/GaN Atomic Concentration Data
20
XPS / ESCA
  • Surface sensitivity
  • Microbeam resolution
  • Depth profiling
  • Elemental composition
  • Some chemical bonding

21
What is XPS / ESCA?
X-ray Photoelectron Spectroscopy (XPS), also
known as Electron Spectroscopy for Chemical
Analysis (ESCA) is a widely used technique to
investigate the chemical composition of surfaces.
22
X-ray Photoelectron SpectroscopySmall Area
Detection
Electrons are extracted only from a narrow solid
angle.
X-ray Beam
X-ray penetration depth 1mm. Electrons can be
excited in this entire volume.
10 nm
1 mm2
X-ray excitation area 1x1 cm2. Electrons are
emitted from this entire area
23
The Photoelectric Process
Ejected Photoelectron
Incident X-ray
  • XPS spectral lines are identified by the shell
    from which the electron was ejected (1s, 2s, 2p,
    etc.).
  • The ejected photoelectron has kinetic energy
  • KEhv-BE-?
  • Following this process, the atom will release
    energy by the emission of an Auger Electron.

Free Electron Level
Conduction Band
Fermi Level
Valence Band
L2,L3
2p
L1
2s
K
1s
24
Auger Relation of Core Hole
Emitted Auger Electron
Free Electron Level
  • L electron falls to fill core level vacancy (step
    1).
  • KLL Auger electron emitted to conserve energy
    released in step 1.
  • The kinetic energy of the emitted Auger electron
    is
  • KEE(K)-E(L2)-E(L3).

Conduction Band
Fermi Level
Valence Band
L2,L3
2p
L1
2s
K
1s
25
Surface Analysis Tools
SSX-100 ESCA on the left, Auger Spectrometer on
the right
26
XPS Spectrum of Carbon
  • XPS can determine the types of carbon present by
    shifts in the binding energy of the C(1s) peak.
    These data show three primary types of carbon
    present in PET. These are C-C, C-O, and O-CO

27
Surface Treatments
  • Control friction, lubrication, and wear
  • Improve corrosion resistance (passivation)
  • Change physical property, e.g., conductivity,
    resistivity, and reflection
  • Alter dimension (flatten, smooth, etc.)
  • Vary appearance, e.g., color and roughness
  • Reduce cost (replace bulk material)

28
Surface Treatment of NiTi
Biomedical Devices and Biomedical Implants SJSU
Guna Selvaduray
29
Surface Treatment of NiTi
Biomedical Devices and Biomedical Implants SJSU
Guna Selvaduray
30
Surface Treatment of NiTi
  • XPS spectra of the Ni(2p) and Ti(2p) signals from
    Nitinol undergoing surface treatments show
    removal of surface Ni from electropolish, and
    oxidation of Ni from chemical and plasma etch.
    Mechanical etch enhances surface Ni.

Biomedical Devices and Biomedical Implants SJSU
Guna Selvaduray
31
(No Transcript)
32
Molecular Self Assembly
33
Self Assembled Monolayers
  • SAMS Self Assembled Monolayers
  • Cast a film onto a surface from a liquid
  • You can also use a spray technique
  • Films spontaneously order / reorder
  • Modifying surface properties yields materials
    with a bulk strength but modified surface
    interaction phase

34
The Self-Assembly Process
A schematic of SAM (n-alkanethiol CH3(CH2)nSH
molecules) formation on a Au(111) sample.
The self-assembly process. An n-alkane thiol is
added to an ethanol solution (0.001 M). A gold
(111) surface is immersed in the solution and the
self-assembled structure rapidly evolves. A
properly assembled monolayer on gold (111)
typically exhibits a lattice.
35
SAM Technology Platform
  • SAM reagents are used for electrochemical,
    optical and other detection systems.
    Self-Assembled Monolayers (SAMs) are
    unidirectional layers formed on a solid surface
    by spontaneous organization of molecules.
  • Using functionally derivatized C10 monolayer,
    surfaces can be prepared with active chemistry
    for binding analytes.

http//www.dojindo.com/sam/SAM.html
36
SAM Surface Derivatization
  • Biomolecules (green) functionalized with biotin
    groups (red) can be selectively immobilized onto
    a gold surface using a streptavidin linker (blue)
    bound to a mixed biotinylated thiol / ethylene
    glycol thiol self-assembled monolayer.

http//www.chm.ulaval.ca/chm10139/peter/figures4.d
oc
37
SAMs C10 Imaging with AFM
http//sibener-group.uchicago.edu/has/sam2.html
38
AES vs. XPS?
  • AES needs an electrically conductive substrate
    metals and semiconductors
  • XPS can analyze polymers and metals
  • AES very small area imaging
  • XPS somewhat small area imaging
  • Depth profiling of thin films, faster by AES, but
    only for conductive materials

39
Image Analysis
  • AFM
  • Atomic Force Microscopy
  • SEM - EDX
  • Scanning Electron Microscopy
  • Energy Dispersive Wavelength X-Ray
  • TEM
  • Transmission Electron Microscope

40
Seeing the Nano World
  • Because visible light has wavelengths that are
    hundreds of nanometers long we can not use
    optical microscopes to see into the nano world.
    Atoms are like boats on a sea compared to light
    waves.

41
AFM
  • Atomic Force Microscope (AFM)
  • Scanning Tunneling Microscope (STM)
  • Scanning Probe Microscopy (SPM)
  • Magnetic Force Microscopy (MFM)
  • Lateral Force Microscopy (LFM)

42
AFM Instrumentation
PNI Nano-R AFM Instrumentation as used at
Foothill College
43
What is an SPM?
  • An SPM is a mechanical imaging instrument in
    which a small, lt 1 µm, probe is scanned over a
    surface. By monitoring the motion of the probe,
    the surface topography and/or images of surface
    physical properties are measured with an SPM.

z
y
z
44
A Family of Microscopes
45
Many Imaging Modes
DC Contact Mode - Hard Samples - Probes gt 20
nm
  • AC Close Contact Mode - Soft Samples - Sharp
    Probe lt20nm

Material Sensing Modes Lateral
Force Vibrating Phase
46
Crystal Scanner
Point and Scan Crystal Sensor Stage
Automation Software
47
AFM Stage Assembly
AFM Stage for sample orientation, with scanner
and optics
48
AFM Light Lever Force Sensor
49
Nano-R Stage
High Resolution Video Microscope
Scanner
Light LeverCrystal
Sample Puck
X-Y Stage(in granite block)
50
High ResolutionVideo Microscope
Optical Microscope
Software control of videomicroscope functions
51
Easy Sample Load
Load and Unload Sample Positions
Sample Puck
52
Video Optical Microscope
Laser AlignmentFeature Location
53
Information Technology DVD
54
Consumer Razor Blade
55
Consumer Applications
56
Metrology of Metals
  • AFM can be used to understand surface morphology.
  • This material was prepared using a spray / cast
    technique.

57
Metrology of Structures
  • The pattern and depth of this micro lens can be
    determined using an AFM.
  • This helps in both development and process
    control.

58
NanoMechanics- MEMS
59
SEM Techniques
  • Scanning Electron Microscopy (SEM)
  • Wavelength Dispersive X-Ray (WDX)
  • Primary electron imaging
  • Secondary electron imaging
  • X-ray (WDX) elemental mapping

60
SEM Principles of Operation
  • In an electron microscope, electrons are
    accelerated in a vacuum until their wavelength is
    extremely short. The higher the voltage the
    shorter the wavelengths.
  • Beams of these fast-moving electrons are focused
    on an object and are absorbed or scattered by the
    object so as to form an image on an
    electron-sensitive photographic plate

61
SEM Principles of Operation
  • Electron beam
  • Electron gun
  • Anode
  • Magnetic lens
  • Scanning coils
  • Secondary electron detector
  • Stage and specimen

http//mse.iastate.edu/microscopy/path2.html
62
SEM Principles of Operation
http//mse.iastate.edu/microscopy/beaminteractions
.html
63
SEM Principles of Operation
http//mse.iastate.edu/microscopy/proimage.html
64
SEM Imaging
  • Imaging of microscopic scale objects in high
    resolution

65
SEM Instrument
66
SEM AFM Comparison
SEM AFM Wide range of sample
roughness True 3D image Operated in low to high
vacuum Vacuum, Air or
Liquid
67
Imaging Applications
  • Imaging individual atoms.
  • Imaging of surface materials.
  • Imaging of nanotubes.

68
TEM Diagram
  • The TEM works like a slide projector. A beam of
    electron is shined though the surface with the
    transmitted electrons projector on a screen.

69
TEM in Use
  • The drawback is the sample must be very thin for
    the electrons to pass through and the sample has
    to be able to withstand the high energy electrons
    and a strong vacuum.

70
X-Ray Diffraction
  • X-Ray diffraction is an important tool in the
    characterization of nanostructures.
  • It is the principle means by which the atomic
    structure of materials can be determined.

71
Summary of Techniques
  • Surface techniques
  • AES
  • ESCA / XPS
  • Deeper techniques
  • RBS and PIXE
  • Ion techniques
  • SIMS

72
Materials Analysis Review
  • What is it you need to know?
  • What volume of material?
  • Elemental information?
  • Chemical information?
  • Molecular information?
  • Structural information?

73
Analyst Skills
  • Instrument skills
  • Analytical reasoning ability
  • Materials science
  • Process knowledge
  • Industry knowledge

74
Commercial Laboratories
  • Evans Analytical Group
  • Center for Microanalysis of Materials
  • Stanford Nanofabrication Facility
  • Failure Analysis Associates
  • Balaz Analytical Laboratories

75
Summary
  • Nanostructures are very small
  • You need tools that characterize atoms and the
    world (neighborhood) of an atom
  • Composition and chemistry
  • Molecular bonding information
  • Structural information
  • Film thickness especially
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