Surface work function studies in porous silicon

Band structure studies in porous silicon provide useful information about the operative phenomenon responsible for its room temperature photoluminescence. We have measured the average surface work function, using a retarding field diode method in ultrahigh vacuum conditions, for porous silicon having different crystalline columnar dimensions. The average crystallite size was determined by grazing angle x-ray diffraction measurements; whereas the band gap was estimated from the photoluminescence measurements. Based on these results, different empirical band structural models are reviewed. Photoconductivity measurements in porous silicon also insinuate that the electrical resistivity of the surface of porous silicon is manipulated by the silicon complexes present on the surface. It has been concluded that, in addition to the quantum confinement, the surface molecular species dominantly control the behavior of photoluminescence and average surface work function of porous silicon. (C) 1998 American Vacuum Society.