Structural investigations of metal-semiconductor surfaces

A complete understanding of surface phenomena in electronic materials requires knowledge of the atomic arrangement. Recent results for surface atomic structures using high resolution transmission electron microscopy and transmission electron diffraction are presented. These results include atomic level imaging of complex structures such as Si(111)-(7 x 7) showing not just the adatoms but also the buried dimers, and accurate refinements of surface models based on electron diffraction data. A new concept for surface phases is reviewed, replacing the typical simple diagrams showing the temperature versus coverage regime with a phase diagram obeying Gibbs phase rules (for the system Au on Si(111), submonolayer regime). Another important development, Direct Methods, constitutes a new technique to find an initial estimate for the refinement of surface atomic models. Using a Minimum Relative Entropy method, the Direct Methods approach was successful for the case of transmission electron as well as X-ray diffraction data. Its application to solving a number of surface reconstructions is discussed. (C) 1999 Elsevier Science Ltd. All rights reserved.