Molecular dynamics simulation of impurities in nanocrystalline diamond grain boundaries

Nanocrystalline diamond films grown on Si substrates at 800 degrees C from hydrogen-poor ;plasmas have a number of highly desirable mechanical and electronic properties. Impurities were found by SIMS measurements to be uniformly distributed throughout the thickness of the films at a level of 10(17) - 10(18) cm(-3). It is likely that the impurities are located at the grain boundaries, which play a crucial role in controlling important characteristics of the films, such as electrical conductivity and electron emission. Density-functional based tight-binding (DFTB) molecular dynamics simulations were performed for diamond high-energy high-angle (100) twist grain boundaries with impurities such as N, Si and H.