Epitaxial growth of ultrathin ZrO2(111) films on Pt(111)

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 O-2 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), (root 19 x root 19) R23.4A degrees and (5x5) structures coexisted on the surface. As the coverage increased, the (root 19 x root 19) R23.4A degrees structure developed with increasing degree of long-range order, while the (5x5) structure gradually faded. When the coverage reached > 6 ML, a continuous ZrO2(111) film was formed with a (1x1) surface LEED pattern coexisting with a (2x2) 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.