Structural characterization of boron nitride films

The microstructure of amorphous hydrogenated boron nitride films, with nominal composition B3N:H, is characterized with respect to hydrogen bonding and distribution by combined application of nuclear-magnetic-resonance (NMR) spectroscopy, electron-spin-resonance spectroscopy, and evolved gas analysis. Previous infrared studies on annealed films suggest that hydrogen is present in multiple configurations; qualitatively, low-temperature anneals (∼600 °C) deplete N-H moieties whereas B-H configurations are depleted at higher temperatures (∼1050 °C). Gas analysis corroborates these results, showing H2 peaks at ∼570 and ∼950 °C. From an analysis of nuclear dipolar couplings extracted from the 1H NMR spectra, it is concluded that the hydrogen is essentially randomly distributed as monohydrides; other configurations, such as dihydrides and monohydride clusters, are estimated to be less than 20% total. Furthermore, the 1H NMR spectra show no evidence of molecular H2 trapped in the films. In a film exposed to a high x-ray dose (∼30 kJ cm−3), it was determined that the damage was equivalent to 1 unpaired electron spin per 175 B3N:H units. The 1H NMR linewidth did not change after irradiation, which suggests that the hydrogen spatial distribution was unaffected.