Role of high nitrogen-vacancy concentration on the photoluminescence and Raman spectra of diamond

TL;DR

This study investigates how high concentrations of nitrogen-vacancy centers in diamond influence its photoluminescence and Raman spectra, revealing the dominance of NV fluorescence at high densities and the limitations of Raman spectroscopy for characterization.

Contribution

It provides new insights into the spectral behavior of diamonds with high NV densities, highlighting the interplay between Raman scattering and NV fluorescence under different excitation wavelengths.

Findings

High NV densities lead to NV fluorescence dominating spectra.

Raman signals are overwhelmed at the highest NV concentrations.

NIR excitation can reveal Raman features despite high NV fluorescence.

Abstract

We present 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). With green red, and near infrared (NIR) light excitation, we demonstrate 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 we observe a combination of Raman scattering from the diamond lattice and fluorescence from the NV centers, while for the highest NV densities the Raman signals from diamond are completely overwhelmed by the intense NVs 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 naive belief that Raman scattering enables complete characterisation of a diamond crystalline sample.