Boron nitride coatings by chemical vapor deposition from borazine

Boron nitride coatings were prepared from borazine as the single source precursor containing stoichiometric boron and nitrogen by hot-wall chemical vapor deposition (CVD) in a low deposition temperature range from 800 °C to 900 °C, with a total pressure of 1 kPa. The chemical and phase compositions, morphologies and structures of the coatings were investigated. The coatings deposited at 800 °C still contained some residual N–H, whereas the coatings prepared at 900 °C were comparatively pure BN. The surface of the as-deposited coatings exhibited a pebble-like and compact structure, and the cross-sectional morphology of the coatings showed a laminar structure. While the as-deposited coatings had a turbostratic structure as evidenced from the XRD and TEM examinations, the turbostratic BN crystallized into hexagonal BN by heat treatment at temperatures above 1400 °C. The as-deposited coatings had a preferential orientation near the coating/graphite substrate interface in which the (002) basal planes organized parallel to the surface of the substrate.