We report results from cathodoluminescence spectroscopy of boron nitride films grown on Si(100) substrates by ion-source-assisted magnetron sputtering of a hexagonal BN target. Three main peaks are observed in the near-band-gap region for hexagonal boron nitride films at energies of 4.90,5.31, and 5.50 eV We also report deep-level emission spectra of predominantly cubic boron nitride films which are correlated with sample growth conditions. In particular we show that the emission intensity, position, and linewidth are strongly dependent on the substrate bias voltage used during sample growth.

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We report the growth of cubic boron nitride (cBN) films by magnetron sputtering on Si (100) substrates. The films are grown in the presence of negative substrate bias voltages and a nitrogen plasma produced by an electron cyclotron resonance source. We find evidence for a sharp low-voltage threshold in the substrate bias (-105 V) beyond which the samples are predominantly cBN. The structural quality of the cBN films is optimized in a narrow range of voltages near this threshold. We discuss the important role of energetic ions in the formation of cBN in light of recent theoretical findings.

Soft x-ray core-level photoabsorption has been measured from three forms of boron nitride, namely the hexagonal (hBN), cubic (cBN), and incoherent (iBN) phases. The B 1s and N 1s photoabsorption spectra of the hBN sample show evidence of both σ*- and π*-empty states, indicative of sp2 bonding, while the cBN absorption spectra exhibits only sp3 bonding in absorption features characteristic of the zincblende structure. The incoherent phase of BN in the form of a thin film on a Si substrate possesses σ* and π* states similar to hBN. The B 1s π* absorption features of the iBN film show an angular dependence which suggests that the microstructure consists of hexagonal-phase layer planes oriented normal to the BN/Si interface.

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