Structural investigation of theZnSe(001)−c(2×2)surface

Zinc selenide is a model system for II-VI compound semiconductors. The geometric structure of the clean $\mathrm{}\left(001\right)\mathrm{}-c(2\mathrm{}\times 2)$ surface has recently been the subject of intense debate. We report here a surface x-ray-diffraction study on the $\mathrm{ZnSe}\mathrm{}\left(001\right)\mathrm{}-c(2\mathrm{}\times 2)$ surface performed under ultrahigh vacuum using synchrotron radiation which reveals the precise atomic geometry. The results are in excellent agreement with the Zn-vacancy model proposed earlier on the basis of density-functional theory calculations and unequivocally establish the correct equilibrium surface structure.