Kittel, M., Polcik, M., Terborg, R., Hoeft, J.T., Baumgartel, P., Bradshaw, A.M., Toomes, R.L., Kang, J.H., Woodruff, D.P., Pascal, M., Lamont, C.L.A. and Rotenberg, E. (2001) The structure of oxygen on Cu(100) at low and high coverages. Surface Science, 470 (3). p. 311. ISSN 00396028

The local adsorption structure of oxygen on Cu(1 0 0) has been studied using O 1s scanned-energy mode photoelectron diffraction. A detailed quantitative determination of the structure of the 0.5 ML (√2×2√2)R45°-O ordered phase confirms the missing-row character of this reconstruction and agrees well with earlier structural determinations of this phase by other methods, the adsorbed O atoms lying only approximately 0.1 Å above the outermost Cu layer. At much lower coverages, the results indicate that the O atoms adopt unreconstructed hollow sites at a significantly larger O–Cu layer spacing, but with some form of local disorder. The best fit to these data is achieved with a two-site model involving O atoms at Cu–O layer spacings of 0.41 and 0.70 Å in hollow sites; these two sites (also implied by an earlier electron-energy-loss study) are proposed to be associated with edge and centre positions in very small c(2×2) domains as seen in a recent scanning tunnelling microscopy investigation.