Role of High Nitrogen‐Vacancy Concentration on the Photoluminescence and Raman Spectra of Diamond

A photoluminescence (PL) and Raman spectroscopy study of various diamond samples that have high concentrations of nitrogen‐vacancy (NV) color centers up to multiple parts per million (ppm) is presented. With green, red, and near‐infrared (NIR) light excitation, it is demonstrated that while for samples with a low density of NV centers the signals are primarily dominated by Raman scattering from the diamond lattice, for higher density of NVs, a combination of Raman scattering from the diamond lattice and fluorescence from the NV centers is observed, while for the highest NV densities the Raman signals from diamond are completely overwhelmed by the intense NV's fluorescence. However, under NIR excitation, Raman diamond signatures can be observed for some diamonds. These observations reveal different roles of two mechanisms of light emission and contradict the naïve belief that Raman scattering enables the complete characterization of a diamond crystalline sample.