SI K-EDGE X-RAY-ABSORPTION FINE-STRUCTURE STUDIES OF POROUS SILICON

X-ray absorption fine structure (XAFS) spectra of porous Si prepared b y the anodization of a Si wafer in aqueous HF solution have been obtai ned with synchrotron radiation. The Si K-edge near-edge X-ray absorpti on fine structure and extended X-ray absorption fine structures clearl y show that porous silicon samples that have been exposed to the ambie nt environment (untreated) have an oxide layer, while the ''clean'' (t reated) porous Si sample regenerated by HF treatment shows some degrad ation in its crystallinity. Noticeable differences in the XAFS between porous Si and crystalline Si are noted. The results and implications of this observation and the chemistry leading to the formation of surf ace oxygen compound are discussed.