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
Surface Characterization Techniques
●   A: Scanning Probe Methods
●   B: Low Energy Scattering
●   C: Near Surface Method
●   D: Analytical Methods in Electron Microscopy
●   E: Other Methods
         Scanning Probe Techniques
• a: Scanning Probe Techniques
         Scanning Probe Techniques
• a: Scanning Probe Techniques
        Scanning Probe Techniques
• b: Atomic Force Microscopy (Scanning Force
  Microscopy)
           Low Energy Scattering

• a: Low Energy Electron Diffraction
          Low Energy Scattering
• a: Low Energy Electron Diffraction
       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.
                   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.
            Near Surface Methods
• a: Rutherford Back Scattering (RBS)
         Near Surface Methods
• b: Secondary-Ion Mass Spectroscopy (SIMS)
           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.
              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.
          Near Surface Methods
• e: Auger Electron Spectroscopy
            Near Surface Methods
• e: Auger Electron Spectroscopy
    Analytical Methods in Electron Microscopy

●   a: Energy-Dispersive Spectrometry (EDS)
    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
            Other Techniques
• a: Temperature Programmed Desorption (TPD)
     2: Surface Crystallography
●   A: Lower-Miller-Index Crystal Planes
●   B: Surface Reconstruction
●   C: Higher-Miller-Index Crystal Planes
     2: Surface Crystallography
A: Lower-Miller-Index Crystal Planes
Observe from LEED
     2: Surface Crystallography
A: Lower-Miller-Index Crystal Planes
Observe from LEED- For Ordered Adsorbate Periodicity
     2: Surface Crystallography
A: Lower-Miller-Index Crystal Planes
Observe from LEED- For Ordered Adsorbate Periodicity
   2: Surface Crystallography
• A: Lower-Miller-Index Crystal Planes
Unit Cell Notation          Matrix Notation:




                                Wood’s Notation
   2: Surface Crystallography
• B: Surface Reconstruction
Reconstruction on Metal
     2: Surface Crystallography
• B: Surface Reconstruction
Reconstruction on Semiconductors
S(100) (2x1) Reconstruction
   2: Surface Crystallography
• C: Higher-Miller-Index Crystal Planes
Surface Defects:
   2: Surface Crystallography
• C: Higher-Miller-Index Crystal Planes
   2: Surface Crystallography
• C: Higher-Miller-Index Crystal Planes




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

				
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posted:11/17/2011
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