STRUCTURE OF PROTOTYPICAL SEMICONDUCTOR SURFACES AND INTERFACES INVESTIGATED BY PHOTOEMISSION EXTENDED X-RAY-ABSORPTION FINE-STRUCTURE (PEXAFS)

Extended X-ray absorption fine structure (EXAFS) has been known for ha lf a century. However, using synchrotron radiation, it has developed i nto a powerful tool for determining the atomic structure of a wide var iety of surfaces and interfaces. The power of this technique lies in i ts sensitivity to the local environment of a particular element. Photo emission extended X-ray absorption fine structure (PEXAFS) is a new va riation of electron detection surface EXAFS (SEXAFS) using photoemissi on spectroscopy in the constant initial state mode. Due to small escap e depths, a very high surface sensitivity is achieved. Other major adv antages of this new technique include (i) an improved signal/noise rat io allowing very short data collection times, which is an especially u seful feature for short lifetime surfaces, and (ii) double-checking in teratomic distances. Combined with core level and valence band photoem ission spectroscopies. PEXAFS provides the exceptional ability to prob e the atomic geometry and the electronic structure at the same time an d for the same surface. It thus gives access to important issues, such as (i) surface reconstruction and/or relaxation, (ii) bonding nature, (iii) adsorption site and (iv) initial interface formation. Furthermo re, it could be used to clarify photoemission core level shift origin by allowing one to discriminate structural changes from other causes a s initial or final state effects. This article reviews the latest PEXA FS investigations for model elemental (silicon) and compound (indium p hosphide) semiconductor surfaces and their interfaces with alkali meta ls, antimony, aluminum, bismuth and silver.