Visible photoluminescence and its mechanisms from a-SiOx : H films with different stoichiometry

The photoluminescence (PL) properties of H-rich amorphous silicon oxide thi n films prepared by dual-plasma chemical vapor deposition have been studied . The three commonly reported PL bands centered around 1.7, 2.1 and 2.9 eV have been detected from the same type of a-SiOx: H material, only by varyin g the oxygen content (x approximate to 1.35, 1.65, 2). In order to characte rize the PL bands, the samples in as-prepared and annealed states up to 900 degrees C have been analyzed by XPS, FT-IR, gas effusion, ESR and ellipsom etry. Temperature quenching experiments are crucial to distinguish the 1.7 eV band, fully consistent with a bandtail-to-bandtail transition, from radi ative defect luminescence mechanisms attributed either to defects related t o Si-OH groups (2.9 eV) or to oxygen vacancy defects (2.1 eV). (C) 1999 Els evier Science B.V. All rights reserved.