Use of different excitation wavelengths for the analysis of CVD diamond by laser Raman spectroscopy

Raman spectroscopy has been shown to be an accurate technique for the qualitative characterisation of chemical vapour deposited (CVD) diamond films. The intensities of the diamond and non-diamond components in the spectrum vary with the wavelength of the laser excitation. This shows that laser Raman at different wavelengths can be used as a selective probe for the different constituents of the deposited film. In the present work, this selectivity has been used to examine the effect of methane concentration during growth on the Raman spectra of CVD diamond. Diamond films were deposited on single crystal Si(100) wafer substrates by microwave plasma enhanced, and hot filament assisted CVD. Methane concentrations of 0.36–2.16% in hydrogen were used as the feedstock. Laser wavelengths ranging from the ultraviolet (244 nm) to the infra-red (780 nm) were used to perform Raman spectroscopy on the deposited diamond films. Scanning electron microscopy (SEM) was used to determine the morphology of the films and related to the Raman spectra.