Growth and Surface Structure of Zinc Oxide Layers on a Pd(111) Surface

• Published in: Journal of physical chemistry. C Vol. 114; no. 36; pp. 15432 - 15439
• Main Authors: Weirum, G, Barcaro, G, Fortunelli, A, Weber, F, Schennach, R, Surnev, S, Netzer, F. P
• Format: Journal Article
• Language: English
• Published: American Chemical Society 16.09.2010
• Subjects: C: Surfaces, Interfaces, Catalysis
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp104620n

The growth and geometric structure of ultrathin zinc oxide films on Pd(111) has been studied by scanning tunneling microscopy, low-energy electron diffraction, and density functional theory calculations. For sub-monolayer coverages, depending on the oxygen pressure, two well-ordered zinc oxide phases with (4 × 4) and (6 × 6) coincidence structures form, which are attributed to H-terminated Zn6O5 and graphite-like Zn6O6 layers, respectively. The (6 × 6) phase exhibits a pronounced oxygen pressure dependence: at low p(O2) a well-ordered (6 × 6) two-dimensional array of O vacancies develops, yielding a layer with a formal Zn25O24 stoichiometry, while at high p(O2) the Zn6O6 monolayer transforms into bilayer islands. For oxide coverages up to 4 monolayers the graphite-like Zn6O6 structure is thermodynamically the most stable phase over a large range of oxygen chemical potentials, before it converges to the bulk-type wurtzite structure. Under oxygen-poor conditions a compressed overlayer of Zn adatoms can be stabilized on top of the Zn6O6 structure.