Atomic-like emissions in UV region from hexagonal boron nitride crystal powders

Abstract

Hexagonal boron nitride (h-BN) crystal powders were characterized for structural and optical properties. Deep UV photoluminescence (PL) spectroscopy was employed for the optical characterization. We studied the effect of annealing on the PL emissions from the h-BN crystal powders. We observed sharp atomic-like PL emission lines in the UV spectral region at 4.10 and 4.12 eV along with their longitudinal optical phonon replicas from the samples annealed in ambient air around 700 °C for 1 h which were not present in the unannealed samples. Our study suggests that the point defects related to the atomic-like emissions are generated during the annealing process of the h-BN. Based on the theoretical calculation results, the atomic-like emissions in the UV region have been assigned to a carbon dimer defect. The annealed h-BN powder samples also exhibited pronounced phonon assisted band-edge emission peaks at 5.78 and 5.89 eV, and enhanced emission intensity of the major peak at 5.49 eV in the low temperature (8 K) PL spectrum.