Growth mechanism for epitaxial cubic boron nitride films on diamond substrates by ion beam assisted deposition

Abstract

Cubic boron nitride (c-BN) films were grown on highly (001)-oriented chemical vapour deposited diamond films at various substrate temperatures ( T s) ranging from 420 to 1000 °C by using ion beam assisted deposition (IBAD). The resulting c-BN films were characterized by Fourier transformed infrared spectroscopy, high-resolution transmission electron microscopy, Rutherford backscattering spectroscopy as well as X-ray diffraction. The results demonstrate that the epitaxial growth of c-BN films on diamond can be realized only at high values of T s (approx. 900 °C), while at, e.g. 420 °C, an intermediate hexagonal BN layer is formed between the substrate and the c-BN film as it is usually observed for c-BN growth on top of Si. This may be due to the amorphization or graphitization (radiation damage) of the diamond surface at low T s under the assisting ion bombardment during c-BN nucleation. The plasmon energies of the diamond substrates that were held at various temperatures and bombarded by a mixture of argon and nitrogen ions were determined from in situ low-energy electron energy loss spectra. The results indicate that at higher T s values radiation damage can be annealed out thereby maintaining an ordered substrate surface, hence allowing epitaxial growth of c-BN.