Investigation on the microstructure and optical properties of c-axis oriented nanocrystalline hexagonal BN films fabricated by hot-filament chemical vapor deposition

Nanocrystalline hexagonal boron nitride (hBN) films are grown on Si(001) substrates by hot-filament chemical vapor deposition. X-ray diffraction analyses indicated that hBN films are highly c-axis oriented and the line width of the (0002) diffraction peak is 1.57°. Fourier transform infrared investigation revealed that the dominant absorption peak of (0001) oriented hBN film is at approximately 1384 cm− 1, which is from the in-plane B-N stretching vibration mode of hBN. Photoluminescence spectroscopic measurement demonstrates the strong near-band-edge ultraviolet emission centered at 326 nm, which is ascribed to the nanocrystalline nature of hBN film. The optical band gap of hBN film surveyed by photoluminescence excitation is approximately 3.84 eV and is 0.47 eV wider than that of hexagonal ZnO. The wider band gap and the higher chemical stability of c-axis oriented hBN compared with that of wurtzite ZnO would make it a more suitable candidate material in the fabrication of surface acoustic wave devices.