Physical structure of light-emitting porous polycrystalline silicon thin films

This paper reports the surface electronic structure of light-emitting porous polycrystalline silicon (PPS) using Xray photoelectron spectroscopy (XPS). We find that the PPS films with strong photoluminescence (PL) effect can only be observed in thin film with trace amount of silicon nanoclusters and the luminescence can be enhanced remarkably with proper passivation of the PPS surface. Incomplete oxidation of silicon (Si^3+ or Si^2+) does not lead to visible PL. We further estimate that the average size of silicon nanoclusters is in the range of 20-30 A in the sample having PL emission. (C) 1999 Elsevicr Science Ltd. All rights reserved.