Nitridation of diamond(111) surface by density functional theory

Density functional theory was employed to examine the adsorption and thermal evolution of nitrogen species on diamond(111) impacted by microwave N-2 plasma. On bare domains of diamond, as represented by the models of C(111)-2 x 1 and graphite-like C(111), N-2(ad) is identified as the major surface species; the desorption of N-2(ad) proceeds on both models via a concerted process of breaking two C-N bonds. By contrast, there is evidence of the formation of (NH)(2)(ad) via the insertion reaction of microwave N-2 plasma on hydrogenated domains of diamond, as represented by the models of C(111)-2 x 1-H and C(111)-1 x 1-H. Interestingly, contrasting dynamics of desorption of (NH)(2)(ad) are presented on these two models, that is, via sequential breaking of two C-N bonds on C(111)-2 x 1-H and via concerted breaking of both C-N bonds on C(111)-1 x 1-H. Our results demonstrate that the observed diversity of surface nitrogen species in composition, bonding, vibration, and desorption in prior experiments is linked to domains of a variety of surface terminations and reconstructions on diamond(111).