The properties of native defects and impurities in diamond were investigated via large-scale band structure and Car-Parrinello calculations. In diamond, the activation energy for self-diffusion was very high (9eV) in the intrinsic material but decreased by up to 3eV in either p- or n-type material. Phosphorus, lithium and sodium were shallow donors, but their solubilities were very low, which makes them unsuitable for incorporation into diamond via in-diffusion. Instead, kinetic trapping during growth or ion implantation had to be used. Considering the stability at the dopant site, substitutional phosphorus was expected to diffuse by the vacancy mechanism and to have a high activation energy by analogy to self-diffusion. Both lithium and sodium diffuse through the interstitial channel. Lithium was a relatively fast diffuser while sodium should be stable up to moderately high temperatures. For nitrogen in diamond, the well-known (111) distortion was found to be due to the interaction of the fully occupied nitrogen lone pair with the dangling bond of the C(111) atom. The single electron associated with the center resides in an anti-bonding orbital formed from the dangling hybrid and the nitrogen lone pair. This orbital has most of its amplitude on the carbon atom.

Theory of Native Defects, Doping and Diffusion in Diamond and Silicon Carbide. Bernholc, J., Kajihara, S.A., Wang, C., Antonelli, A., Davis, R.F.: Materials Science and Engineering B, 1992, 11[1-4], 265-72