The structures of sulphur on Pd(111) studied by X-ray standing wavefield absorption and surface EXAFS

• Published in: Surface science 1998-08, Vol.410 (2), p.321-329
• Main Authors: Dhanak, V.R, Shard, A.G, Cowie, B.C.C, Santoni, A
• Format: Article
• Language: English
• Subjects: Chemisorption; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Low index single crystal surfaces; Normal incidence standing X-ray wavefield (NIXSW); Palladium; Physics; Solid surfaces and solid-solid interfaces; Solid-fluid interfaces; Sulphur; Surface extended X-ray absorption fine structure (SEXAFS); Surface relaxation and reconstruction; Surface structure; Surface structure and topography; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); X-ray absorption
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/S0039-6028(98)00332-X

The surface structures of ( 3 × 3 ) R30°-S and ( 7 × 7 ) R19.1°-S on Pd(111) have been investigated by normal incidence X-ray standing wave (NIXSW) absorption and surface extended X-ray absorption fine structure (SEXAFS). NIXSW measurements show that the most likely site of S adsorption in the ( 3 × 3 ) R30° phase is the threefold “fcc” hollow. The location of the S atoms at the “fcc” hollow site is consistent with S adsorption on the neighbouring fcc (111) transition metal surfaces. SEXAFS analysis revealed a S–Pd nearest neighbour bond distance of 2.28±0.04 Å. The results for the ( 7 × 7 ) R19.1° phase suggest that the structure involves a mixed S–Pd overlayer, with the S–Pd vertical layer spacing equal to the Pd bulk 〈111〉 spacing.