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Chemistry LibreTexts

6: Overlayer Structures & Surface Diffraction

  • Page ID
    25353
    • 6.1: Classification of Overlayer Structures
      Adsorbed species on single crystal surfaces are frequently found to exhibit long-range ordering ; that is to say that the adsorbed species form a well-defined overlayer structure. Each particular structure may only exist over a limited coverage range of the adsorbate, and in some adsorbate/substrate systems a whole progression of adsorbate structures are formed as the surface coverage is gradually increased. This section deals with the classification of such ordered structures.
    • 6.2: Low Energy Electron Diffraction (LEED)
      LEED is the principal technique for the determination of surface structures. It may be used in one of two ways: Qualitatively : where the diffraction pattern is recorded and analysis of the spot positions yields information on the size, symmetry and rotational alignment of the adsorbate unit cell with respect to the substrate unit cell. Quantitatively : where the intensities of the various diffracted beams are recorded as a function of the incident electron beam energy to generate so-called I-V
    • 6.3: Reflection High Energy Electron Diffraction (RHEED)
      To extract surface structural information from the diffraction of high energy electrons, therefore, the technique has to be adapted and the easiest way of doing this is to use a reflection geometry in which the electron beam is incident at a very grazing angle - it is then known as Reflection High Energy Electron Diffraction (RHEED).
    • 6.4: Examples - Surface Structures

    Contributors

    • Roger Nix (Queen Mary, University of London)