Micro-Raman analysis of the cross-section of a diamond film prepared by hot-filament chemical vapor deposition

Raman micro-spectroscopy using exciting light with an approximately 2-mu m diameter exciting spot was undertaken to investigate the micro-structure of cross-section of a 100-mu m thick diamond film prepared by hot-filament chemical vapor deposition (HFCVD). The Raman spectra exhibited different features with changing position, suggesting that the composition of crystalline diamond, amorphous carbon and graphitic phases varied in the HFCVD process. The presence of a broad band and high background intensity in the spectra near the substrate surface was attributed to the amorphous carbon synthesized in the nucleation process of the film. A decreasing proportion of sp(2)-bond structure in the amorphous carbon phase with increasing film thickness was believed to account for the decline in the intensity of the 1200-1600-cm(-1) band. The different composition of the diamond grains and of the grain boundaries in the him was shown in the Raman spectra obtained from different positions at the same cross-sectional thickness by scanning the exciting light parallel to the surface of the film. (C) 2000 Published by Elsevier Science S.A. All rights reserved.