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 SiO x films with 0.88 < x < 2 incorporating a few atomic percent of H and N. The question of IR band assignment in a ‐ SiO x 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 ( O 2 ) SiH and ( O 3 ) 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 Si 0 and Si 3 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 ( Si 3 ) progressively expands as x → 2 , at the expense of the silicon‐rich phase ( Si 0 ) . The volume ratio of the Si 3 environment increases smoothly without drastic changes in the microscopic structure, and is already dominant at x = 1.53 .