Surface Characterization Techniques and Surface Crystallography

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Surface Characterization Techniques and Surface
Crystallography

• 1 Surface Characterization Techniques
• A Scanning Probe Method
• B Low Energy Scattering
• C Near Surface Method
• D Analytical Methods in Electron Microscopy
• E E Other Methods
• 2 Surface Crystallography
• A Lower-Miller-Index Crystal Planes
• B Surface Reconstruction
• C Higher-Miller-Index Crystal Planes

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Surface Characterization Techniques

• A Scanning Probe Methods
• B Low Energy Scattering
• C Near Surface Method
• D Analytical Methods in Electron Microscopy
• E Other Methods

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Scanning Probe Techniques

• a Scanning Probe Techniques

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Scanning Probe Techniques

• a Scanning Probe Techniques

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Scanning Probe Techniques

• b Atomic Force Microscopy (Scanning Force
  Microscopy)

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Low Energy Scattering

• a Low Energy Electron Diffraction

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Low Energy Scattering

• a Low Energy Electron Diffraction

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Low Energy Scattering

• b Low-Energy Ion Scattering (LEIS)
• The surface under study is hit with a low
  energy beam (ca. 500-2000 eV) of noble gas ions,
  usually helium. The collisions that take place
  can be considered as elastic. LEIS has the
  characteristic of being sensitive only to the
  outermost surface composition.

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Near Surface Methods

• a Rutherford Back Scattering (RBS)

Ions of a high kinetic energy (typically 1-3MeV)
are directed at the sample. The incident ions are
elastically scattered from the atoms in the
sample. The number of scattered ions and their
energy is measured. This data provides
information on the composition of the sample, the
distribution of those components and the
thickness of the sample. The incident ions are
positively charged He atoms and the detective
depths can be several micrometers.
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Near Surface Methods

• a Rutherford Back Scattering (RBS)

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Near Surface Methods

• b Secondary-Ion Mass Spectroscopy (SIMS)

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Near Surface Methods

• c X-Ray Photoelectron Spectroscopy (XPS)

using soft x-ray (200-2000 eV) radiation to
examine core-levels
a sampling depth on the order of 5 nm.
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Near Surface Methods

• d Ultraviolet Photoelectron Spectroscopy (UPS)

Using vacuum UV (10-45 eV) radiation to examine
valence levels
1 The electronic structure of solids - detailed
angle resolved studies permit the complete band
structure to be mapped out in k-space. 2 the
adsorption of relatively simple molecules on
metals - by comparison of the molecular orbitals
of the adsorbed species with those of both the
isolated molecule and with calculations.
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Near Surface Methods

• e Auger Electron Spectroscopy

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Near Surface Methods

• e Auger Electron Spectroscopy

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Analytical Methods in Electron Microscopy

• a Energy-Dispersive Spectrometry (EDS)

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Analytical Methods in Electron Microscopy

• b Electron Energy Loss Spectroscopy (EELS)

By examining energy losses at high resolution
(about 30 meV), as in HREELS, data concerning the
vibrations of molecules on surfaces can be
determined
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Other Techniques

• a Temperature Programmed Desorption (TPD)

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2 Surface Crystallography

• A Lower-Miller-Index Crystal Planes
• B Surface Reconstruction
• C Higher-Miller-Index Crystal Planes

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2 Surface Crystallography
A Lower-Miller-Index Crystal Planes Observe from
LEED
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2 Surface Crystallography
A Lower-Miller-Index Crystal Planes Observe from
LEED- For Ordered Adsorbate Periodicity
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2 Surface Crystallography
A Lower-Miller-Index Crystal Planes Observe from
LEED- For Ordered Adsorbate Periodicity
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2 Surface Crystallography

• A Lower-Miller-Index Crystal Planes
• Unit Cell Notation

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2 Surface Crystallography

• B Surface Reconstruction
• Reconstruction on Metal

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2 Surface Crystallography

• B Surface Reconstruction
• Reconstruction on Semiconductors

S(100) (2x1) Reconstruction
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2 Surface Crystallography

• C Higher-Miller-Index Crystal Planes
• Surface Defects

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2 Surface Crystallography

• C Higher-Miller-Index Crystal Planes

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2 Surface Crystallography

• C Higher-Miller-Index Crystal Planes

G. A. Somorjai, et al Surface Science 92(1980)
489