Influence of radiation interference on the shape of Raman spectra for amorphous hydrogen-free diamondlike carbon films

The influence of interference on the shape of Raman spectra from thin films is considered. High refractive index, low absorption and sufficient film thickness combined with high reflection from a substrate surface are the conditions to enhance the interference distortion of the Raman spectra. In the case of an amorphous hydrogen-free diamondlike carbon film deposited onto a highly reflecting aluminum layer, the interference dramatically distorts the ratio of Raman intensities at 500 and 1550 cm(-1), by about a factor of four when the spectra are registered by using a conventional backscattering geometry. The effect is smaller but clearly noticeable for ordinary silicon-substrate samples as well. The magnitude of the interference modification is strongly influenced by geometrical factors such as the direction and polarization of the detected Raman scattered light. (C) 1996 American Institute of Physics.