Core-level photoabsorption study of defects and metastable bonding configurations in boron nitride

Abstract

A comprehensive study of different local bonding environments in boron nitride bulk and thin films has been performed by core-level photoabsorption. Several features not present in crystalline reference samples are found in the absorption spectra of the thin films. These are identified as nitrogen vacancies in the hexagonal bonding of BN, nitrogen interstitials, boron clustering, ${\mathrm{sp}}^{3}$-like metastable phases, and ${\mathrm{sp}}^{3}$ phases. Quantitative information on the concentration and distribution of point defects is easily extracted from the photoabsorption data and is discussed with regard to the formation of additional phases, the B:N ratio in the films, and compared with a random model of defect formation. Information on the stability of the bonding environments is gained by annealing the thin films. Modification of the orientation of the ${\mathrm{sp}}^{2}$ hexagonal planes is attained by ion bombardment and annealing, and is monitored by angle-resolved photoabsorption.