Effect of substrate surface on the structure and electronic properties of cubic boron nitride films

Abstract

Cubic boron nitride (c-BN) films were prepared by mass-selected ion beam deposition (MSIBD) technique. The effects of substrate surface roughness were investigated by boron and nitrogen k-edge x-ray absorption near-edge structure, x-ray diffraction, and atomic force microscopy. All the films are a mixture of nanocrystalline sp3-bonded c-BN and sp2-bonded BN phases. The substrate with a rough surface causes a decrease of the c-BN phase content of the film on it. A significant large lattice contraction of the c-BN crystallites in the films, relative to the bulk, is observed. It is also found that the electronic structure of the nanocrystalline c-BN films by MSIBD technique is somewhat different from that of microcrystalline c-BN∕h-BN references. We attribute the effect of the nature of the substrate on the morphology and structure of the c-BN films to the orientation of sp2-bonded graphitic BN basal plane on the top surface of the films during their growth, and the lattice contraction and energy band structure modification of c-BN films to the large compressive stress, respectively.