Quantification of nitrogen in HPHT diamond: A synergistic approach combining FTIR and EPR validation

Nitrogen in diamond is a prerequisite for the formation of nitrogen-vacancy (NV) center, making precise quantification of nitrogen concentration critical for diamond-based sensors and quantum devices. This study aims to address the significant quantitative deviation (approximately 61 %) caused by the nitrogen doping inhomogeneity in high-pressure and high-temperature (HPHT) diamonds and the spatial resolution constraints of fourier transform infrared spectroscopy (FTIR) characterization through a FTIR averaging method across the entire diamond slice region to quantify nitrogen concentration. Quantitative analysis demonstrates that for HPHT diamond, a single region in nitrogen concentration determined by FTIR exhibits excellent reproducibility with a standard deviation of approximately 6 %, while the standard deviation across the entire diamond slice is reduced to approximately 20 %. Moreover, combining electron paramagnetic resonance (EPR) method, the average nitrogen concentration values measured by FTIR across the entire diamond slice region exhibit good linear correlation (R² > 0.98) with EPR results, indirectly validating the reliability of our characterization approach used in this paper for nitrogen quantification. This study can provide a reference scheme for the quantitative analysis of nitrogen in HPHT diamonds and lay a solid foundation for the controlled preparation and optimization of quantum sensing materials based on HPHT diamonds in future research.