Effect of deposition temperature on the alignment of hexagonal laminates in turbostratic boron nitride thin film

The deposition behavior of turbostratic boron nitride (t-BN) films was investigated with the focus on its microstructure variation in relation to deposition temperature substrate bias voltage. BN films were deposited using the unbalanced magnetron sputtering method. Thin (100μm) Si strips (3×40mm²) coated with a nanocrystalline diamond thin layer were used as substrates. A BN target was used, which was connected to a radio frequency power supply set at 400W. A pulsed direct current power supply connected to a substrate holder was used for negative biasing. The deposition pressure was 0.27Pa with a flow of Ar (18sccm)-N₂ (2sccm) mixed gas. Only t-BN films were deposited with the substrate bias less than -100V irrespective of the deposition temperature. The orientation of (0002) t-BN laminate alignment changed from normal to parallel to the substrate surface with increased deposition temperature. High resolution transmission electron microscopy and Fourier transform infrared spectroscopy confirmed such behavior. However, the application of bias voltage made the (0002) laminates align normal to the substrate surface even at high deposition temperatures. The films tended to react with moisture in an ambient atmosphere as confirmed by the appearance of OH absorption peak in the FTIR spectrum. The measured OH absorption intensity was not influenced by the variation of deposition variables.