785 nm Raman Spectroscopy of CVD Diamond Films

Abstract

AbstractRaman spectroscopy is a powerful technique often used to study CVD diamond films, however, very little work has been reported for the Raman study of CVD diamond films using near infrared (785 nm) excitation. Here, we report that when using 785 nm excitation, the Raman spectra from thin polycrystalline diamond films exhibit a multitude of peaks (over 30) ranging from 400-3000 cm−1. These features are too sharp to be photoluminescence, and are a function of film thickness. For films >30 μm thick, freestanding films, and for films grown in diamond substrates the Raman peaks disappear, suggesting that the laser is probing the disordered small-grained interface between the diamond and substrate. Some of the peaks change in relative intensity with time (‘blinking’), and the spectra are very sensitive to position on the substrate – this is reminiscent of the behaviour seen in SERS spectra.