The adsorption and manipulation of K atoms on an hydroxylated TiO2(110)-(1x1) surface was studied using low-temperature non-contact atomic force microscopy. At low coverages, first-principles GGA+U calculations revealed favorable adsorption sites that were consistent with the experimentally observed adsorption positions on the upper-threefold hollow site, in which the K atom was bound to two bridging-oxygen (Obr) and one in-plane oxygen atoms, forming an ionic bond with three oxygen by transferring almost one of the K 4s electrons to the substrate. The K atoms could be manipulated preferentially along the [001] direction over the Obr row by the tip through attractive force. Density functional theory calculations have provided diffusion paths for the adsorbed K atoms, which indicate a channel that provides ease of diffusion for a single K atom along the Obr rows associated with an energy barrier of 0.21eV.

Alkali-Metal Adsorption and Manipulation on a Hydroxylated TiO2(110) Surface using Atomic Force Microscopy. Yurtsever, A., Sugimoto, Y., Abe, M., Matsunaga, K., Tanaka, I., Morita, S.: Physical Review B, 2011, 84[8], 085413