ELECTRONIC AND ATOMIC-STRUCTURE OF METASTABLE PHASES OF BORON-NITRIDEUSING CORE-LEVEL PHOTOABSORPTION

Soft x-ray core-level photoabsorption has been measured from three for ms of boron nitride, namely the hexagonal (hBN), cubic (cBN), and inco herent (iBN) phases. The B 1s and N 1s photoabsorption spectra of the hBN sample show evidence of both sigma- and pi*-empty states, indicat ive of sp2 bonding, while the cBN absorption spectra exhibits only sp3 bonding in absorption features characteristic of the zincblende struc ture. The incoherent phase of BN in the form of a thin film on a Si su bstrate possesses sigma and pi* states similar to hBN. The B 1s pi* a bsorption features of the iBN film show an angular dependence which su ggests that the microstructure consists of hexagonal-phase layer plane s oriented normal to the BN/Si interface.