STRUCTURAL MODIFICATIONS AND TEMPERATURE STABILITY OF SILICON INCORPORATED DIAMOND-LIKE A-C-H FILMS

Thermal stability of diamond-like carbon is still a problem which limi ts the potential applications of this material. With the aim of obtain ing a material with increased stability, the behaviour of silicon inco rporated hydrogenated amorphous carbon films (a-C1-xSix:H) under therm al annealing was investigated. Results show that the observed effects can be divided in two groups: low temperature (T < 400 degrees C) and high temperature (T > 400 degrees C) effects. In contrast to what is o bserved in case of pure a-C:H, several of the properties of the films were found to change in the low temperature range. A detailed analysis of the infrared absorption spectra showed that the density of sp(3) C -H bonds is increased while the olefinic sp(2) ones are reduced by ann ealing. A shift of the Si-H stretching mode to lower wavenumbers is al so observed, indicating that void elimination may occur due to bond re construction. In this way, a material with reduced spin density, small er residual stress and increased optical gap results, indicating an in creased polymeric character. Upon annealing in the high temperature ra nge, the material degradation processes of hydrogen loss and graphitiz ation start to occur. In the case of films with low silicon content: t he hydrogen effusion process is associated to the graphitization of th e material. As the silicon content is increased, hydrogen effusion is shifted to higher temperatures and graphitization is inhibited due to the increased disorder presented by these films. (C) 1998 Elsevier Sci ence S.A. All rights reserved.