Deposition mechanism of cubic boron nitride

The ion assisted deposition of cubic BN (c-BN) is argued to occur by subplantation, in which low energy ions are implanted below the surface to increase the local density. The situation differs from the case of tetrahedral amorphous carbon (ta-C), because the heteropolar bonding of BN stabilises its crystalline over the amorphous phase. This increases the atomic diffusion energy, which moves the optimum deposition conditions to higher ion energies and higher temperatures. A second difference is the use of ion-assisted deposition which is less efficient than direct subplantation as it creates both interstitials and vacancies rather than just the interstitials which directly increase density.