Ordered epitaxial ZrO2 films were grown on Pt(111) and characterized by low energy electron diffraction (LEED), synchrotron radiation photoemission spectroscopy (SRPES) and X-ray photoelectron spectroscopy (XPS). The films were prepared by vapor deposition of zirconium in an O2 atmosphere followed by annealing under ultra high vacuum. At low coverages, the films grew as discontinuous two-dimentional islands with ordered structures. The size and structure of these islands were dependent on the coverage of ZrO2 films. At coverage <0.5 monolayer (ML), ( 19^(1/2) × 19^(1/2)) R23.4° and (5×5) structures coexisted on the surface. As the coverage increased, the (19^(1/2) × 19^(1/2) ) R23.4° structure developed with increasing degree of long-range order, while the (5×5) structure gradually faded. When the coverage reached >6 ML, a continuous ZrO2(111) film was formed with a (1×1) surface LEED pattern coexisting with a (2×2) pattern. These ordered thin ZrO2 films provide good model surfaces of bulk ZrO2 and can be used for further fundamental studies of the surface chemistry of ZrO2 using modern surface science techniques.
GAO Yan ZHANG Liang PAN YongHe WANG GuoDong XU Yang ZHANG WenHua ZHU JunFa
We report our investigation of the interaction of NO2 with the Au(997)vicinal surface by high-resolution photoelectron spectroscopy using synchrotron radiation as the excitation source.At 170 K,both core-level and valence-band photoemission results illustrate the decomposition of NO2 on the Au(997)surface at low NO2 exposures,forming coadsorbed NO(a)and O(a)species.After annealing at 300 K,NO(a)desorbs from Au(997)whereas O(a)remains on the surface.Upon annealing at 750 K,we observe no signal for adsorbed oxygen on Au(997).These results clearly demonstrate that thermal decomposition of NO2 is an effective method to generate oxygen adatoms on Au(997)under ultrahigh-vacuum conditions.
