LOCAL-STRUCTURE OF POROUS SILICON

Local structural information has been obtained from EXAFS and Laser In duced Mass Analysis (LIMA) of samples of porous silicon produced under various conditions, and these have been correlated with photoluminesc ence excitation spectra. There is evidence for the existence of disord ered silicon-silicon bonds in porous silicon. The XANES show the exist ence of a feature in-between those assigned to Si-Si and Si-O bonding. LIMA indicates that the presence of SiOH correlates strongly with the strength of this peak. In addition, although porous silicon consists of a surface whose roughness is of the order of nanometres, it has bee n possible to obtain depth-profiling from reflected EXAFS (REFLEXAFS) from some samples. The REFLEXAFS XANES again show the additional featu re, the strength of which increases with the intensity of the Si-Si pe ak, that is with depth.