THE ORIGIN OF VISIBLE PHOTOLUMINESCENCE FROM SILICON-OXIDE THIN-FILMSPREPARED BY DUAL-PLASMA CHEMICAL-VAPOR-DEPOSITION

In order to understand the radiative recombination mechanisms in silic on oxides, photoluminescence properties (PL) of H-rich amorphous silic on oxide thin films grown in a dual-plasma chemical vapor deposition r eactor have been related to a number of stoichiometry and structure ch aracterizations (x-ray photoelectron spectroscopy, vibrational spectro scopy, and gas evolution studies). The visible photoluminescence at ro om temperature from a-SiOx:H matrixes with different compositions, inc luding different bonding environments for H atoms, has been studied in the as-deposited and annealed states up to 900 degrees C. Three commo nly reported PL bands centered around 1.7, 2.1, and 2.9 eV have been d etected from the same type of a-SiOx:H material, only by varying the o xygen content (x = 1.35, 1.65, and 2). Temperature quenching experimen ts are crucial to distinguish the 1.7 eV band, fully consistent with b andtail-to-bandtail recombination, from the radiative defect luminesce nce mechanisms attributed either to defects related to Si-OH groups (2 .9 eV) or to oxygen-vacancy defects (2.1 eV). In the latter case, a re d-shift of the PL peak energy as a function of annealing temperature i s probably attributed to some matrix-induced strain effect. (C) 1998 A merican Institute of Physics.