Spontaneous and electron-induced adsorption of oxygen on Au(110)-(1 × 2)

• Published in: Surface science Vol. 511; no. 1-3; pp. 65 - 82
• Main Authors: GOTTFRIED, J. M, SCHMIDT, K. J, SCHROEDER, S. L. M, CHRISTMANN, K
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier Science 10.06.2002; Amsterdam; New York, NY
• Subjects: Adsorption and desorption kinetics; evaporation and condensation; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Physics; Solid-fluid interfaces; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Inorganic adsorbate; Chemisorption; Gold; Activation parameter; Thermally stimulated desorption; Experimental study; Photoelectron spectroscopy; EXAFS spectrometry; Gas solid adsorption; Oxygen molecules; Electron irradiation; Transition elements; Gas solid interface; Metallic adsorbent; Crystal faces; LEED; Radiation damage
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/s0039-6028(02)01555-8

The interaction of dioxygen with a gold(110)-(1 x 2) surface has been investigated between 28 and 700 K by means of thermal desorption spectroscopy (TDS), UV photoelectron spectroscopy (UPS), work function measurements ( Delta Phi ), low-energy electron diffraction (LEED), and near-edge X-ray absorption spectroscopy (NEXAFS). It proves that Au - unlike most of the other metals including its congeners Cu and Ag - does not spontaneously dissociate physisorbed molecular oxygen. Rather, additional activation of the physisorbed O sub 2 either by electron or by photon impact is required to make the oxygen chemisorb. Below 50 K, dioxygen adsorbs readily with a binding energy < 12 kJ/mol, causing a work function decrease of Delta Phi = 0.22 eV at Theta = 1.0 ML. TDS reveals three molecular desorption states with first-order kinetics around 51 and 45 K (first layer), and at 37 K (second layer). A zeroth-order peak around 34 K corresponds to multilayer desorption. Both UPS and NEXAFS exhibit signals typical for physisorbed O sub 2 . Irradiation of physisorbed O sub 2 layers with low-energy electrons or UV photons produces chemisorbed oxygen, providing a convenient possibility for the preparation of chemisorbed oxygen adlayers. The chemisorbed oxygen species is characterized by a single desorption state above 500 K, with second-order kinetics at low coverages ( Theta < 0.25 ML) suggesting adsorbed oxygen atoms. A desorption energy of 140 plus/minus 3 kJ/mol was determined. Another desorption peak around 490 K and at coverages > 1.0 ML is associated with the decomposition of an oxidic species. LEED observations reveal that chemisorbed oxygen destroys the long-range order of the Au substrate surface. Our results provide possible explanations for the 'beam damage' often observed in UPS /LEED experiments with adsorbed dioxygen.