LOCAL-STRUCTURE OF POROUS SILICON

Local structural information has been obtained from extended x-ray-absorption fine-structure measurements on samples of porous silicon produced under various conditions, and these have been correlated with photoluminescence emission and excitation spectra. The x-ray near-edge structure (XANES) shows the existence of a feature in between those assigned to Si-Si and Si-O bonding. Laser-induced mass analysis indicates that the presence of various silicon hydroxides correlates strongly with the strength of this peak. In addition, although porous silicon consists of a surface whose roughness is of the order of nm, it has been possible to obtain depth-profiling reflected x-ray-absorption fine structure (REFLEXAFS) and reflectivity from some samples. The REFLEXAFS XANES again shows the additional feature, the strength of which increases with the intensity of the Si-Si peak, that is, with depth.