SURFACE WORK FUNCTION STUDIES IN POROUS SILICON

Band structure studies in porous silicon provide useful information ab out the operative phenomenon responsible for its room temperature phot oluminescence. We have measured the average surface work function, usi ng a retarding field diode method in ultrahigh vacuum conditions, for porous silicon having different crystalline columnar dimensions. The a verage crystallite size was determined by grazing angle x-ray diffract ion measurements; whereas the band gap was estimated from the photolum inescence measurements. Based on these results, different empirical ba nd structural models are reviewed. Photoconductivity measurements in p orous silicon also insinuate that the electrical resistivity of the su rface of porous silicon is manipulated by the silicon complexes presen t on the surface. It has been concluded that, in addition to the quant um confinement, the surface molecular species dominantly control the b ehavior of photoluminescence and average surface work function of poro us silicon. (C) 1998 American Vacuum Society.