O/Cu(100) Studied By Core Level Spectroscopy

Abstract The chemisorption of oxygen on Cu(100) has been investigated by X-ray photoelectron spectroscopy. From the O 1s binding energy shifts, it is concluded that different adsorption sites are involved in the unreconstructed, disordered and reconstructed (2√2 × √2)R45° phases, respectively. There is an overall binding energy shift of 0.6 eV between θo = 0.13 and θo = 0.50 and the shift is towards higher binding energy for increasing coverage. A strongly asymmetric broadening of the core electron line is observed in the spectra recorded from the (2√2 × √2)R45° phase at elevated temperatures. The full width at half maximum is 1.2 eV at 770 K, compared to 0.80 eV at 300 K. The temperature effects are interpreted as due to vibrational excitations of the adsorbate-substrate complex. No adsorbate-induced ordered structure was observed by LEED except for the (2√2 × √2)R45° pattern.