Spectroscopic characterization of thin SiC films

The electrical, structural and optical properties of thin SiC films were investigated. A new approach based on high temperature annealing of layered carbon-silicon structures was used for the formation of the films. The SiC films were prepared by deposition of 30 nm thick carbon films on crystalline silicon (c-Si) and on porous silicon layers grown on c-Si. The layers were annealed to temperatures between 800 and 1400 degrees C for different annealing times ranging between 15 and 180 s. The structure of the resulting SiC films was analyzed by Raman spectroscopy. The Raman spectra of as-deposited films consist of two broad bands at 1350 and 1580 cm(-1) characteristic of the presence of amorphous carbon. These bands were shifted to lower frequencies in the spectra of annealed layers and were assigned to the hexagonal and cubic SiC phases. The photoluminescence spectra of the studied layers show a broad band at 550 nm. The most intense photoluminescence was observed from non-annealed porous silicon layers covered with thin carbon films. A degradation of the luminescence and a simultaneous increase of the conductivity of the layers with increasing annealing temperature and/or duration of annealing was observed. This behavior strongly suggests the creation of defect states which determine the conductivity of the layers and at the same time act as non-radiative centers. The increase of defect states was explained as originating from the dehydrogenation of the silicon carbide layers by annealing. (C) 1999 Elsevier Science S.A. All rights reserved.