Se-rich phase of ZnSe(100) predicted by total-energy calculations

The relative stability of various ZnSe(100) surface reconstructions is investigated by means of first-principles pseudopotential calculations. A c(2×2) reconstruction with half-monolayer coverage of twofold coordinated Zn atoms is stable in the Zn-rich limit. Under moderately Se-rich conditions, the surface adopts a (2×1) Se-dimer phase. In the extreme Se-rich limit, realizable at low growth temperatures, we predict the stability of a new phase covered with one and a half monolayers of Se. The new structure can account for observed growth rates in atomic layer epitaxy and migration enhanced epitaxy experiments.