Evidence for two oxygen chemisorption sites on the Cr(100) surface at room temperature

Abstract

Abstract The interaction of oxygen with the clean Cr (100) surface has been investigated by work function measurements, angle resolved photoemission spectroscopy and low energy electron diffraction. At low coverages (≈0.15 monolayer (ML)) the adsorbed oxygen is characterized by a work function decrease, a feature at 6.8 eV binding energy in UPS and a weak diffuse C (2 × 2) diffraction pattern. This form of oxygen labeled form a is quite stable at temperatures below 500°C. Upon further exposure at room temperature (⪆0.20 ML) a second form of oxygen labeled form b and characterized by a work function increase and peaks at 3.8 and 5.9 eV at normal photo-emission is identified. It is proposed that oxygen in forms a and b is chemisorbed in the fourfold hollow and on-top sites respectively.