N -type electric conductivity of nitrogen-doped ultrananocrystalline diamond films

The electronic structures of several possible nitrogen-related centers on the diamond surface and in the diamond grain-boundary have been studied using density functional theory approaches with cluster models. The results indicate that the nitrogen-vacancy related complex may be the shallow donor center, and the complexes of nitrogen and dangling bond or nitrogen with a π bond may play the role of compensation centers. Three mechanisms of electric conductivity in ultrananocrystalline diamond films are proposed as the model to explain the recently reported experimental results of both n-type conductivity-temperature and nitrogen-concentration dependences.