STRUCTURAL-ANALYSIS BY INFRARED AND X-RAY PHOTOELECTRON-SPECTROSCOPY OF AMORPHOUS-SILICON PRODUCED BY PLASMA-DEPOSITION

We investigate by IR and XPS a series of amorphous SiOx films with 0.88 < x < 2 incorporating a few atomic percent of H and N. The question of IR band assignment in a-SiOx is reviewed relative to the observed IR spectra. In the material with intermediate oxygen fraction (x < 1), most hydrogen is incorporated as (O)SiH (here the symbol in parentheses corresponds to an atom back-bonded to SiH). The hydrogen incorporation pattern gradually changes to (O2)SiH and (O3)SiH as x increases and consists completely of Si-OH groups for x 2. The analysis of XPS spectra demonstrates that the composition of the films is inhomogeneous at a microscopic scale: the feature of Si 2p core-level spectra originates mainly from Si0 and Si3 groups (e.g., silicon atoms with none and three-bonded oxygen atoms, respectively). The existence of a segregated, oxygen-rich phase is also supported by the peak frequency of Si-O-Si stretching vibration: it is 1030 cm−1 for x = 0.88, a higher value than that predicted for homogeneous oxides of the same composition. The relative volume occupied by the oxygen-rich phase (Si3) progressively expands as x → 2, at the expense of the silicon-rich phase (Si0). The volume ratio of the Si3 environment increases smoothly without drastic changes in the microscopic structure, and is already dominant at x = 1.53. © 1990, The Electrochemical Society, Inc. All rights reserved.