EXAFS and semiconducting amorphous systems

EXAFS spectroscopy has made an important contribution to the study of local structure of amorphous semiconductors. In the past years, great progress has been made thanks to the high accuracy of EXAFS measurements, allowed by the intense third generation synchrotron radiation sources, and the refinement of the analysis techniques. In this paper we briefly review some EXAFS studies about the short range order in Si and Ge based semiconductors. In particular, structure effects deriving from different preparation techniques will be discussed. The relaxation effect of the amorphous network induced by the hydrogenation process in these systems and seen in the reduction of the first shell interatomic distance and disorder parameters, will be also shown. The local structure of some doping impurities of the III and V group in a-Ge hydrogenated thin films will be reported.