Photoluminescence study of N-rich B-doped diamonds grown in NiMnCo solvent before and after annealing

In this paper, we study the PL spectra of N-rich B-doped diamond single crystals grown in NiMnCo solvent, before and after HPHT (high pressure and high temperature) annealing. The PL peaks are observed under 325 nm, 488 nm and 532 nm excitation, respectively. The effects of boron impurity and HPHT annealing on optical centers in N-rich B-doped diamonds are discussed. Before HPHT annealing, as boron incorporation increases in the N-rich diamond, the intensity of the NV− center (627 nm) presents a trend of rising first and then falling. After HPHT annealing at 2.5 GPa and 2000 °C, PL spectra show complex luminescence systems. A series of lines related to Ni–N and Co–N complexes are observed at 602.2 nm, 729.4 nm, 748.8 nm and 542.7 nm in PL spectra under 532 nm and 488 nm excitation. The paramagnetic NE8 center with a ZPL at 793.6 nm appears in the PL spectrum of the N-rich diamond without a boron additive. In the 325 nm excitation PL spectrum of the N-rich B-doped diamond, we also observed the blue luminescence band known as “band-A”. Boron incorporation significantly influences the PL intensity of Ni–N, Co–N and NV− related optical centers in diamonds.