Chemical bonding states and local structures of the oriented hexagonal BCN films synthesized by microwave plasma CVD

In order to synthesize oriented hexagonal boron carbonitride (h-BCN) films, borane-triethylamine complex (C6H18BN) was used as a single-source precursor. The films were deposited on Si (1 0 0) substrate by microwave plasma-enhanced chemical-vapor deposition using CH4+H2 as the carrier gas. The deposition was performed at different microwave powers of 200–500 W at working pressure of 5.0 Torr. The microhardness, estimated by nano-indentation test, of the films was found to be around 4 GPa. Fourier transform infrared spectroscopy (FT-IR) confirmed the formation of hexagonal BCN phase in a short-range order. The chemical composition and the local structures of films were studied by X-ray photoelectron spectroscopy (XPS) and the near-edge X-ray absorption fine structure (NEXAFS) spectroscopic measurements. XPS revealed that B, C and N atoms in the deposited films are in various chemical environments such as B–N, B–C, C–N and B–C–N atomic hybrid configuration. The NEXAFS measurement suggested that the B atoms are bonded not only to the N atoms but also to the C atoms to form various local structures of sp2 B–C–N hybrid configurations. The polarization dependence of NEXAFS suggested that the local structures of the sp2 BCN layers have different atomic orientations to the substrate.