GROWTH AND CHARACTERIZATION OF CUBIC BORON-NITRIDE THIN-FILMS

Boron nitride (BN) thin films have been grown on [100] oriented single crystal Si, diamond, Cu and Ni substrates by ion beam assisted deposi tion using electron beam evaporation of boron together with simultaneo us bombardment by nitrogen and argon ions. Characterization by Fourier -transform infrared spectroscopy and high-resolution transmission elec tron microscopy showed that the films bn Si and diamond consisted of i nitial noncubic (amorphous and hexagonal BN) layers, followed by the g rowth of cubic BN (c-BN). This growth sequence was attributed primaril y to increasing compressive intrinsic stress with increased film thick ness. Increasing the substrate temperature above 400 degrees C led to the onset of c-BN at a greater film thickness while increased ion flux resulted in earlier growth of this phase. These results may be explai ned by the relaxation of the intrinsic stress in the films at higher t emperatures due to increased adatom mobility and to increased intrinsi c stress in the films resulting from increased ion bombardment. Lower temperatures led to mixed phase growth. A minimum substrate temperatur e (200-300 degrees C) is required for nucleation and growth of single phase c-BN by this technique. It is believed that the interstitial Ar observed in Rutherford backscattering spectrometry studies is primaril y responsible for the stress generation in the films. A combination of h-BN and c-BN was deposited on Ni; only h-BN was obtained on Cu subst rates.