Oxygen-Induced Vacancy Formation on a Metal Surface

Abstract

Using scanning tunneling microscopy, low-energy ion scattering, and quantitative low-energy electron diffraction, we find about $17%$ metal vacancies on the oxygen-covered Cr(100) surface. The oxygen atoms occupy all the hollow sites of the first layer, including those neighboring a Cr vacancy. We argue that the vacancy formation is energetically favored and not caused by stress but by electronic effects.