Atomic-scale structure and work function of the K-adsorbed Pd(110)-(1 x 2) surface

The (110) surface of Pd shows a (1 x 2) symmetry when a small amount of K is adsorbed. The structure of this (1 x 2) surface is studied by scanning tunneling microscopy (STM), work function measurement and ab initio density functional theory. Atom-resolved STM images confirm the missing-row reconstruction of the Pd substrate; the K atoms are invisible at coverage of 0.1 monolayer, while they appear as bright rows at 0.3 monolayer. The work functions are calculated for a model in which K atoms are arranged along the grooves of the reconstructed Pd substrate. The calculation agrees very well with the experiment. According to the theory by Tersoff and Hamann, the STM images are analyzed in terms of the local density of states at the Fermi level. The analysis explains why the K atoms become visible with an increase in coverage. (C) 2019 The Japan Society of Applied Physics.