Domain wall formation at the c(2x2)-(2x1) phase transition of the CdTe(001) surface

A specific type of line defect was detected at the temperature-driven c(2 x 2)(2 x 1) phase transition of the CdTe(001) surface, the formation of parallel domain walls in the (2 x 1) phase, using high-resolution low-energy electron diffraction. The domain walls arise because of spontaneous ordering of Cd surface vacancies in the Cd-terminated top layer and yield an effective relaxation of surface strain. Their general relevance for structural and thermodynamic properties of (001) semiconductor surfaces is discussed.