Imaging of sulfur overlayer structures on the Pd(111) surface

• Published in: Surface science 1992-12, Vol.279 (1), p.68-78
• Main Authors: Forbes, Jeffrey G., Gellman, Andrew J., Dunphy, James C., Salmeron, Miquel
• Format: Article
• Language: English
• Subjects: Applied sciences; Chemistry; Exact sciences and technology; General and physical chemistry; Metals. Metallurgy; Solid-gas interface; Surface physical chemistry
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/0039-6028(92)90742-O

We have obtained atomic resolution STM images of both the (√3 × √3) R30° and the (√7 × √7)R19° sulfur overlayer lattices formed on the Pd(111) surface. The images of the (√3 × √3)R30° overlayer are very simple and are consistent with the structure previously determined from LEED analysis. The images of the (√7 × √7)R19° structure on the other hand are surprisingly complex. Within the unit cell which contains ten atoms (seven Pd and three S atoms) we are able to resolve seven atomic scale features. We are faced with the problem of determining which are Pd and which are S. On the basis of comparison of the positions of features in the images with positions of atoms in the Pd(111) surface we propose that two of the sulfur atoms have become incorporated into the subsurface exposing four Pd atoms.