Germanium Adsorption and Initial Growth on SrTiO3(001) Surface: A First-Principles Investigation

Abstract

The initial stages of germanium (Ge) adsorption and heteroepitaxial growth on the SrTiO3 (001) surface have been investigated with first-principles calculations. Our results reveal that the 2 × 1 DL TiO2 reconstruction plays a major role in the Ge chemisorption. This surface reconstruction involves a charge transfer between Ti and O atoms at the surface that locally increases the attractiveness for Ge nucleation. The calculated charge transfer is in good agreement with the core level shift observed by soft X-ray photoemission spectroscopy. Moreover, our potential-energy surface calculations for Ge adatoms on the SrTiO3 (001) 2 × 1 DL TiO2 surface show that the surface diffusions of Ge atoms are highly anisotropic. Ge adatoms are easy to jump from other sites to the most stable site nearby the floating oxygen with energy barriers <0.45 eV. Therefore, the Ge adsorption configuration around surface floating oxygen atom, a particularity of this surface, is identified as the nucleation center of the further Ge...