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Spectral characterization of long-lived luminescence in h-BN nanopowder under UV excitation

Photoluminescence (PL) features of nanostructured h-BN powder are studied in the range of 200-600 nm in millisecond time window. It is found that four PL excitation bands of 4.58, 5.01, 5.29, and 5.77 eV are characteristic of the spectral region at hand. It is shown that the PL emission spectra can be quantitatively described through a superposition of three Gaussian-shaped peaks: 2.6, 3.1, and 3.7 eV. The observable luminescence is established to be due to recombination processes involving centers whose energy levels in the bandgap are formed by oxygen and carbon impurities, as well as nitrogen vacancies and related complexes.