First principles calculation for N[sbnd]Si co-doping in diamond

Abstract

The substituted N and NSix (x = 1, 2, 3, 4) complexes in diamond with possible structures are investigated in terms of the structural models, band structures, density of states, formation energies, ionization energies and binding energies by first-principles calculation. For NSix (x = 0, 1, 2) with stable structures, the electron distribution around N dopant is asymmetrical, and donor levels are deep. Meanwhile, the donor level position, the contribution to donor level, ionization energies are almost equal, since the contribution of Si atoms to the donor levels is almost ignorable. However, for the stable structure NSix with x = 3, the N atom is tetracoordinated, and the contribution of Si to the donor energy level increases. The NSi4 structure (Td symmetry is preserved) has a shallow donor level with an ionization energy of 0.35 eV in formation energy method and 0.44 eV in empirical Marker method. In addition, the formation energies and binding energies increase with the increased Si atoms. This work is helpful for understanding the doping features of NSi complexes in diamond.