Equilibrium Shape of Steps and Islands on Polar II-VI Semiconductors Surfaces

Scanning tunneling microscopy studies of (001) surfaces of partially ionic II-VI compounds show novel surface structures with step and 2D island edges aligned along the $〈100〉$ crystallographic directions. We propose a simplified model incorporating electrostatic interactions in the calculation of the energy of charged steps that could explain why the free energy of $〈100〉$ steps lies below that of the $[110]$ and [11̄0] steps. The energetics of the vicinal surfaces is strongly influenced by this original effect which makes possible the fabrication of staircase and checkerboard templates for growing self-organized nanostructures.