Chemical vapour deposition of thin films of BN onto fused silica and sapphire

Thin films of BN were prepared by chemical vapour deposition onto fused silica and sapphire using the reaction of BCl₃ with NH₃. The temperature of the substrate was varied between 600 and 1100°C. Transparent and smooth films of BN were obtained on fused silica and sapphire at substrate temperatures of 1000–1100°C. The growth rate of the film on sapphire was about 1 μm h^?1, and the growth rate on fused silica was about one-half that on sapphire. The films were chemically inert and adherent to the substrate. The absorption of the BN film was measured at room temperature. In the near-UV region, the main absorption peak was at about 6.2 eV and a sharp drop occurred near 5.8 eV. The sharp drop is attributed to the direct band gap. The photoluminescence of the films was measured at room temperature by excitation with light of wavelength 254 nm. A broad emission with a peak near 360 nm was observed.