Adatom-based (2 × 2 n) reconstruction on Ge(111)

Abstract

Atomic cluster calculations are reported which model adatom generated (2 × 2) and c(2 × 8) reconstruction on the germanium (111) surface, for both the T4 and H3 adsorption sites. The clusters are four atomic layers deep and the positions of atoms in the first three atomic layers are found by minimising the total energy calculated with the MNDO quantum chemical Hamiltonian, according to the prevailing symmetry. Both closed and open shell wavefunctions are considered. We find at least four different electronic states with similar energies but different geometries. The lowest energy is found for the c(2 × 8)H3 configuration with a p-like dangling bond on the rest atom, while for the (2 × 2) structure an s-like dangling bond orbital on the adatom is most favourable.