Growth of an Ultrathin Zirconia Film on Pt3Zr Examined by High-Resolution X-ray Photoelectron Spectroscopy, Temperature-Programmed Desorption, Scanning Tunneling Microscopy, and Density Functional Theory.

摘要: Ultrathin (∼3 A) zirconium oxide films were grown on a single-crystalline Pt3Zr(0001) substrate by oxidation in 1 × 10 −7 mbar of O2 at 673 K, followed annealing temperatures up to 1023 K. The ZrO2 are intended serve as model supports for reforming catalysts and fuel cell anodes. atomic electronic structure composition the determined synchrotron-based high-resolution X-ray photoelectron spectroscopy (HR-XPS) (including depth profiling), low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), density functional theory (DFT) calculations. Oxidation mainly leads ultrathin trilayer (O−Zr−O) alloy; only small area fraction (10−15%) is covered clusters (thickness ∼0.5−10 nm). amount decreases with increasing temperature. Temperature- programmed desorption (TPD) CO was utilized confirm complete coverage Pt3Zr ZrO2, that is, formation closed overlayer. Experiments DFT calculations show core level shifts Zr between those metallic thick (bulklike) ZrO2. Therefore, assignment such XPS substoichiometric ZrOx not necessarily correct, because these signals may equally well arise from or metal/ZrO2 interfaces. Furthermore, our results indicate common approach calculating including final-state effects should be taken care thicker insulating films, clusters, bulk insulators.