ZNSE(100) SURFACE - ATOMIC CONFIGURATIONS, COMPOSITION, AND SURFACE DIPOLE

Chemical composition, core-level line shape, and electron affinity mea surements are performed on the Se-terminated (2X1) and Zn-terminated c (2X2) ZnSe(100) surfaces. The (2X1) reconstruction corresponds to a c omplete monolayer of Se dimers with one filled dangling bond per surfa ce atom. The c(2X2) reconstruction corresponds to a half-monolayer vac ancy structure which leaves twofold-coordinated Zn atoms in the top la yer. The 150-meV decrease in surface electron affinity at the (2X1)--> c(2X2) transition is consistent with this model and results from a dip ole induced by the charge transfer required to empty and fill all cati on and anion dangling bonds on the c (2 X 2) surface, respectively.