The low and high coverage adsorption structure of CO on unreconstructed Ir (100)-(1× 1)

Abstract

The investigation of carbon monoxide (CO) adsorption on the unreconstructed Ir(100)-(1×1) surface under ultra-high vacuum (UHV) conditions is studied with scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), and high-resolution core-level spectroscopy (HRCLS). At a low coverage of 0.5 ML (monolayer), CO molecules adopt a previously documented c(2×2) structure, having CO molecules adsorbed exclusively in the top sites. When the coverage increases to 0.83 ML, a c(6×2) phase is observed having a combination of bridge and top adsorption sites positions. A comprehensive picture of CO adsorption on Ir(100)-(1×1) is presented here by correlating the spectroscopic data with the observed distinct structural formations from STM and LEED.