VISIBLE LUMINESCENCE FROM POROUS SILICON AND SILOXENE

Infrared transmission and Raman spectra of siloxene (Si6O3H6) and porous Si have been analyzed in terms of the structural composition. Siloxene consists of Si6-rings interconnected by oxygen and terminated by hydrogen. and corrugated Si(111)-planes saturated by OH and H. The pronounced photoluminescence of siloxene is mainly related to the Si6-rings. Porous Si shows similar luminescence and almost identical vibrational properties as siloxene, which makes this class of materials a possible candidate for the origin of the luminescence in p-Si. Annealing at temperatures below 300-degrees-C and moderate illumination of siloxene induces the transformation from the Si-plane-like structure to the Si-ring-like structure. Anneal temperatures above 300-degrees-C and intense illumination of both siloxene and p-Si leads to an effusion of hydrogen and an irreversible oxidation of the samples.