A theoretical study of nitrogen-induced effects on initial steps of diamond CVD growth

An investigation based on an ultra-soft, pseudo-potential, density functional theory (DFT) method, using a generalized gradient approximation (GGA) under periodic boundary conditions, is performed in order to investigate the effect of substitutional nitrogen on the CH3 adsorption and the H abstraction from the adsorbed CH3 species. Both (111) and (100)-2x1 surface are considered with 4 and 6 substitutional N positions, respectively. For the two surface orientations, no strong effect of N is generally observed when positioning it within the first C layer (i.e., surface layer). The only exception is for N in one of three investigated first layer positions within the (100) surface, for which a spontaneous beta-scission occurs as a result of the H abstraction reaction. For N in the second carbon layer, the CH3 adsorption reaction is calculated to be strongly disfavored, whilst the H abstraction reaction is markedly improved.