title: Ba deposition and oxidation on theta-Al2O3/NiAl(100) ultrathin films. Part I: Anaerobic deposition conditions.
abstract: Room-temperature Ba deposition on an oxygen-terminated theta-Al(2)O(3)/NiAl(100) ultrathin film substrate under ultrahigh vacuum (UHV) conditions is studied using X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and temperature programmed desorption (TPD) techniques. In addition, Ba oxidation by the ions of the alumina substrate at 300 K < T < 1200 K in the absence of a gas-phase oxidizing agent is investigated. Our results indicate that at room temperature Ba grows in a layer-by-layer fashion for the first two layers, and Ba is partially oxidized. Annealing at T < 700 K results in further oxidation of the Ba species, whereas annealing at higher temperatures leads to loss of Ba from the surface via desorption and subsurface diffusion.
authors.affiliation: Institute for Interfacial Catalysis, Pacific Northwest National Laboratory, P.O. Box 999, MSIN K8-93, Richland, Washington 99352, USA.
authors.forename: Emrah
authors.initials: E
authors.lastname: Ozensoy
authors.forename: Charles H F
authors.initials: CH
authors.lastname: Peden
authors.forename: János
authors.initials: J
authors.lastname: Szanyi