Spectroscopic characterization of thin SiC films

The electrical, structural and optical properties of thin SiC films were in vestigated. A new approach based on high temperature annealing of layered c arbon-silicon structures was used for the formation of the films. The SiC f ilms 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 anne aling times ranging between 15 and 180 s. The structure of the resulting Si C films was analyzed by Raman spectroscopy. The Raman spectra of as-deposit ed 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 freq uencies in the spectra of annealed layers and were assigned to the hexagona l and cubic SiC phases. The photoluminescence spectra of the studied layers show a broad band at 550 nm. The most intense photoluminescence was observ ed from non-annealed porous silicon layers covered with thin carbon films. A degradation of the luminescence and a simultaneous increase of the conduc tivity 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 sam e time act as non-radiative centers. The increase of defect states was expl ained as originating from the dehydrogenation of the silicon carbide layers by annealing. (C) 1999 Elsevier Science S.A. All rights reserved.