Effect of Pressure on Characteristics of Diamonds Synthesized under High Temperature and High Pressure in Boron-Nitrogen Co-doped Systems

Abstract

This study systematically investigates the effect of synthesis pressure on the characteristics of diamond crystals grown by the high temperature and high pressure (HPHT) method in a boron-nitrogen co-doping system. Diamond single crystals were synthesized within a pressure range of 5.7-6.5 GPa using a NiMnCo alloy as the catalyst, with simultaneous introduction of nitrogen and boron sources. Comprehensive characterization was performed using Fourier-transform infrared (FTIR) and Raman spectroscopies. The results show that pressure is a key parameter for tuning the competitive doping between boron and nitrogen. As the pressure increases from 5.7 GPa to 6.5 GPa, the nitrogen content in diamond decreases significantly while the incorporation efficiency of boron is markedly enhanced. This is directly reflected in the co-doped crystals by a gradual fading of the macroscopic green color with increasing pressure, and the FTIR results further confirm this conclusion. Raman spectroscopy further reveals that increasing pressure under co-doping conditions helps improve crystal quality, as evidenced by a reduction in the full width at half maximum (FWHM) of the characteristic diamond peak. Moreover, pressure variation does not introduce new types of luminescent defects; the main luminescence in all samples originates from NV- color centers. This study finds that increasing the system pressure promotes boron incorporation while suppressing nitrogen uptake. This provides key experimental evidence for the targeted tuning of diamond semiconductor properties (e.g., the fabrication of p-type semiconductors) via HPHT process parameters, and also offers valuable insights for understanding the mantle origin of natural diamonds.