The surface composition, structure and oxygen-induced (2x1) reconstruction of Cu3Pt(110)

The surface composition, structure, and oxygen-induced reconstruction of Cu3Pt(110) have been investigated by low-energy ion scattering, recoiling spectrometry, and low-energy electron diffraction. The surface composition of the top two layers was determined from Li+ single-scattering intensities using selective scattering geometries with calibration measurements on reference standards. Under thermal equilibrium conditions, the measurements consistently showed a surface composition of 82% Cu-18% Pt in the first layer, while the second layer was composed almost entirely of Cu. From computer simulations and analysis of the shadowing critical edges, the first interlayer spacing was found to be contracted by about 6+/-2%. whereas the surface Pt atoms were buckled outward by 0.1+/-0.06 Angstrom. Adsorption of oxygen on the clean Cu3Pt(110) surface at room temperature followed by subsequent annealing leads to a (2 x 1) reconstruction. By Li+ ion scattering and negative O- recoil measurements the oxygen-induced structure was determined to be a missing-row type reconstruction which involves loss of Pt from the first layer in a thermally activated place exchange with Cu atoms. The first interlayer spacing was expanded by 23+/-10% relative to the ideal spacing, while the O atoms were located 0.1+/-0.1 Angstrom below the first Cu layer. The structural features found are discussed and compared with previous results on the Cu(110)-(2 x 1)-O and Cu3Au(110)-(2 x 1)-O surfaces. (C) 1998 Elsevier Science B.V. All rights reserved.