Structural and electronic properties of the Zn_0.5Cd_0.5Se(100) surface

The chemical composition, atomic structure and electron affinity of Zn_0.5Cd_0.5Se(100) grown by molecular beam epitaxy and prepared by Se-decapping are investigated. The Se-terminated surface exhibits a (2 × 1) reconstruction which corresponds to a complete monolayer of Se dimers. The cation-terminated surface exhibits a (1 × 1) structure tentatively attributed to a vacancy structure similar to that of the c(2 × 2) Zn-terminated ZnSe surface, but randomized by the non-periodic distribution of Zn and Cd. The evolution of the electron affinity of the surface is consistent with the formation of a surface dipole induced by a cation-to-anion charge transfer which fills (empties) all anion (cation) dangling bonds. Finally, preferential desorption of Cd is observed for temperatures in excess of 370°C.