Pulsed laser deposition of cubic boron nitride films on silicon substrates

Quasicrystalline cubic boron nitride (cBN) thin films have been deposited on clean single crystal silicon substrates by the pulsed laser deposition technique. Different chamber gases (N₂ and NH₃) at pressures between 10^-3 and 800 mTorr were employed for the deposition processes. Typically, boron-rich films were obtained, but the boron/nitrogen ratio was reduced when nitrogen or nitrogen/ammonia gases were incorporated during the deposition process. Under a wide range of deposition conditions, the films exhibited a quasicrystalline cubic phase near the film-substrate interface (∼150 Å thick). A completely amorphous phase was observed beyond this region, suggesting that the substrate plays an important role in the crystallization of cBN thin films.