Stability of nitrogen incorporated Al_2O_3 surfaces: Formation of A1N layers by oxygen desorption

摘要

The incorporation of nitrogen on Al_2O_3(0001) and (1102) surfaces is theoretically investigated on the basis of total-energy electronic-structure calculations within the density functional theory. The calculated surface energies as functions of oxygen and nitrogen chemical potentials reveal that under pregrowth conditions the O atoms of Al_2O_3 surfaces can be replaced by N atoms. Moreover, we find that the outermost 0 atoms tend to desorb from the surface and A1N layers are consequently formed on Al_2O_3 surfaces. This im plies that the desorption of oxygen is crucial for the nitridation process. The structures of nitrogen incorpo rated Al_2O_3 surfaces obtained in the present study are consistent with those observed in the experiments.