Coverage Effects and the Nature of the Metal−Sulfur Bond in S/Au(111):  High-Resolution Photoemission and Density-Functional Studies

• Published in: Journal of the American Chemical Society Vol. 125; no. 1; pp. 276 - 285
• Main Authors: Rodriguez, José A, Dvorak, Joseph, Jirsak, Tomas, Liu, Gang, Hrbek, Jan, Aray, Yosslen, González, Carlos
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 08.01.2003
• Subjects: Adsorbed layers and thin films; Adsorption and desorption kinetics; evaporation and condensation; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Electron and ion emission by liquids and solids; impact phenomena; Exact sciences and technology; Photoemission and photoelectron spectra; Physics; Solid-fluid interfaces; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Inorganic adsorbate; Gold; Adsorption energy; Adsorption site; Adsorption capacity; Surface electron state; Theoretical study; Thermally stimulated desorption; Experimental study; Gas solid adsorption; Electron correlations; Electronic structure; Transition elements; Photoemission; Gas solid interface; Metallic adsorbent; Density functional method; Adsorption structure; Crystal faces; Sulfur; Local density approximation
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja021007e

The bonding of sulfur to surfaces of gold is an important subject in several areas of chemistry, physics, and materials science. Synchrotron-based high-resolution photoemission and first-principles density-functional (DF) slab calculations were used to study the interaction of sulfur with a well-defined Au(111) surface and polycrystalline gold. Our experimental and theoretical results show a complex behavior for the sulfur/Au(111) interface as a function of coverage and temperature. At small sulfur coverages, the adsorption of S on fcc hollow sites of the gold substrate is energetically more favorable than adsorption on bridge or a-top sites. Under these conditions, S behaves as a weak electron acceptor but substantially reduces the density-of-states that gold exhibits near the Fermi edge. As the sulfur coverage increases, there is a weakening of the Au−S bonds (with a simultaneous reduction in the Au → S charge transfer and a modification in the S sp hybridization) that facilitates changes in adsorption site and eventually leads to S−S bonding. At sulfur coverages above 0.4 ML, S2 and not atomic S is the more stable species on the gold surface. Formation of S n (n > 2) species occurs at sulfur coverages higher than a monolayer. Very similar trends were observed for the adsorption of sulfur on polycrystalline surfaces of gold. The S atoms bonded to Au(111) display a unique mobility/reactivity not seen on surfaces of early or late transition metals.