Identification of O atoms on a Cu(110) surface by scanning tunneling microscope light emission spectra

We have identified the adsorption site of O atoms on the Cu(110)-O surface by studying the light emission spectra from individual atomic sites induced by scanning tunneling microscope (STM). Although the STM image contrast reverses depending on the tip condition, the emission spectrum from the oxygen site shows the same characteristic peaks, regardless of the image contrast. These characteristic peaks are identified with the electronic density of states associated with the O $2p$ orbitals.