Thermally stimulated processes in the luminescence of carbon-related defects for h-BN micropowder

With band-to-band (5.9 eV) excitation of a micropowder of hexagonal boron nitride with a content of carbon and oxygen impurities of <= 3.5 at. %, the peculiarities of the luminescence at 3.76 eV (330 non) in the temperature range of 300-873 K have been studied. For thermally activated processes responsible for peaks at 331, 353 and 597 K in the spectral band, the kinetic parameters such as activation energy, the effective frequency factor, and kinetics order have been estimated. For this, curve fitting, the initial rise and E-A - T-stop methods as thermally stimulated luminescence (TSL) techniques have been utilized. Analysis of the experimental temperature dependencies of the photoluminescence (PL) intensity has been carried out within the framework of the Mott relation with two independent quenching channels and taking the TSL contribution observed into account. The processes of PL temperature quenching have been shown to proceed by an external mechanism and to be characterized by energies of E-Q = 1.43 and 1.39 eV. It has been concluded that the calculated values correlate with the level positions in the forbidden gap for two possible energy configurations of the C-N -center for M- and K-valleys in the first Brillouin zone.