Germanium adsorption on SrTiO ₃ (001) 2×1 surface: A density functional theory study

Integrating germanium on Si is one of the major challenges of epitaxial growth and presents important applicative interest. Recently, SrTiO ₃ was adopted as a buffer layer to accommodate the mismatch between Ge and Si. Germanium can take its bulk lattice parameter as soon as the growth begins without threading defects on SrTiO ₃ surface. However, the details of Ge adsorption on SrTiO ₃ surface are not clear. In present work, the electronic structures of Ge deposited on the SrTiO ₃ (001) 2×1 Double Layer (DL) TiO ₂ surfaces were investigated by means of density functional theory calculations. Several stable adsorption sites are identified. It is found that the germanium adsorption shows site selectivity and causes noticeable surface distortion. The charge transfer from germanium atom to surface contributes to the formation of strong Ge-O bondings and surface metallization.