First-principles study of lithium adsorption on Si(1 0 0)2 × 1 and Ge(1 0 0)2 × 1 surface at 1.0 monolayer coverage

First-principles calculations based on density functional theory have been carried out to determine the atomic structure and electronic properties of the Si(1 0 0)2 × 1-Li and Ge(1 0 0)2 × 1-Li adsorption systems at 1.0 monolayer (ML) coverage. For the Si(1 0 0)2 × 1-Li chemisorption system, the lowest energetic configuration is that one Li atom resides at the T3′ (which is displaced along the positive y-axis from the valley bridge (T3) site by 0.90 Å) and the other resides at pedestal (HH) site. For the Ge(1 0 0)2 × 1-Li chemisorption system, the most stable configuration is found to be that one Li atom resides at HH site and the other one will penetrate deeply into the substrate surface. Chemisorption of the lithium atoms is found to result in a minimum energy configuration characterized by symmetric dimers in agreement with the results of high-resolution core-level photoelectron spectroscopy. The adsorption systems show semiconducting surface characterization.