Energetics of adsorbed hydrogen and surface germanium on stepped Six Ge1-x (100)-(2×1) surfaces

Abstract

The energetics of adsorbed hydrogen and surface germanium on vicinal silicon-germanium surfaces is important in understanding the growth of a silicon-germanium film at the atomic scale. By using plane wave pseudopotential density functional theory methods, we have calculated the molecular hydrogen adsorption energy at silicon-germanium sites at and near four different types of steps that are important. We have also calculated the relative energies for a germanium atom that is found at various sites in the vicinity of these steps. It is known that adsorbed hydrogen is more likely to be found at step sites than on terraces for pure silicon surfaces. However, our calculations show that the distribution of adsorbed hydrogen is considerably more uniform on silicon-germanium surfaces. Our calculations also show that for clean surfaces, germanium substitution is energetically favored at step sites, while for hydrogenated surfaces, the distribution of surface germanium atoms is likely to be uniform. These results show that the equilibrium distributions of adsorbed hydrogen and surface germanium atoms are correlated to each of their concentrations. © 2008 The American Physical Society.