Adsorption of k on Au(110) and Ag(110) surfaces: A scanning tunneling microscopy and density functional theory study

Abstract

Adsorption of alkali metals on surfaces is of importance in nanoscience, electrochemistry and heterogeneous catalysis. Here we use scanning tunneling microscopy (STM) and density functional theory (DFT) to study the behaviors of K adsorption on Au(110) and Ag(110) at low coverage. K atoms adsorbed in the reconstructed grooves are visible in our high-resolution STM images. Owing to the charge transfer between K and Au(110) surface, the positively charged K atoms exhibit low density of states near the Fermi level, resulting in a depression morphology in STM images. Furthermore, most of the K atoms adsorbed in the reconstructed grooves have a K-K distance 3 or 3.5 times of the surface periodicity in the [1 −1 0] direction. Density functional theory calculations reveal almost equivalent adsorption energies at the hollow and bridge sites, implying a negligible diffusion barrier along the reconstructed grooves. A positive charge about 0.80–0.86 e is calculated for K adsorbed on all Au(110)-(1 × 2), Au(110)-(1 × 3) and Ag(110)-(1 × 2) surfaces.