Electronic and energetic properties of Ge(110) pentagons

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The electronic and energetic properties of the elementary building block, i.e. a five-membered atom ring (pentagon), of the Ge(110) surface was studied by scanning tunneling microscopy and spectroscopy at room temperature. The Ge(110) surface is composed of three types of domains: two ordered domains ((16×2) and c(8×10)) and a disordered domain. The elementary building block of all three domains is a pentagon. Scanning tunneling spectra recorded on the (16×2), c(8×10) and disordered domains are very similar and reveal three well-defined electronic states. Two electronic states are located at 1.1eV and 0.3eV below the Fermi level respectively, whereas the third electronic state is located at 0.4eV above the Fermi level. The electronic states at −0.3eV and 0.4eV can be ascribed to the pentagons, whilst we tentatively assigned the electronic state at −1.1eV to a Ge–Ge back bond or trough state. In addition, we have analyzed the straight 112¯ oriented step edges. From the kink density and kink–kink distance distributions we extracted the nearest neighbor interaction energy between the pentagons, which exhibit a strong preference to occur in twins, as well as the strain relaxation energy along the pentagon-twin chains.