An Influence of X-Ray Irradiation on Mid-Bandgap Luminescence of Boron Nitride Epitaxial Layers

Samples of boron nitride (BN) in the form of an exfoliated monolayer, epitaxial layers grown on sapphire, anda powder with micrometer grains were studied in a luminescence experiment connected with irradiation of sampleswith X-rays. The luminescence excited with photons with the wavelength of 488 nm was shown to span over a broadband from a filter cut-off at 550 nm to about 850 nm. The intensity of luminescence showed a monoexponentialdecrease both before and after irradiation with X-rays, but this dynamics slowed down after irradiation to an extentdependent on the X-ray dose. This indicates possible application of BN in dosimetry of X-rays. An influence ofsapphire substrates on photoluminescence dynamics was also studied. We show that this influence is very strongin the case of layers with thickness of a few nm and can be disregarded when the thickness is equal to a few tensof nm.