LOCAL-STRUCTURE OF POROUS SILICON

Local structural information has been obtained from extended x-ray-abs orption fine-structure measurements on samples of porous silicon produ ced under various conditions, and these have been correlated with phot oluminescence emission and excitation spectra. The x-ray near-edge str ucture (XANES) shows the existence of a feature in between those assig ned to Si-Si and Si-O bonding. Laser-induced mass analysis indicates t hat the presence of various silicon hydroxides correlates strongly wit h the strength of this peak. In addition, although porous silicon cons ists of a surface whose roughness is of the order of nm, it has been p ossible to obtain depth-profiling reflected x-ray-absorption fine stru cture (REFLEXAFS) and reflectivity from some samples. The REFLEXAFS XA NES again shows the additional feature, the strength of which increase s with the intensity of the Si-Si peak, that is, with depth.