Growth, structure and annealing behaviour of epitaxial ZrO2 films on Pt(1 1 1)

For future investigations of catalytic reactions on sulfated ZrO2 surfaces by means of scanning tunneling microscopy (STM), ZrO2 films are prepared on Pt(1 1 1) and characterized by STM and low-energy electron diffraction (LEED). The films are prepared by vapor deposition of Zr in an O2 atmosphere followed by annealing (also in an O2 atmosphere). Conditions are searched where well-ordered, continuous and smooth ZrO2 films are formed. Depositing the films according to literature data at room temperature [Surf. Sci. 237 (1990) 166] yields films with hillock morphology which decay during annealing and loose continuity. The desired film perfection is attained, however, if the films are deposited at 470 K and postannealed at 950 K. Continuous films are obtained displaying large terraces and a clear p(1 × 1) ZrO2(1 1 1) LEED pattern. A splitting of the LEED spots reveals that the films are slightly rotated with respect to Pt(1 1 1). However, annealing the films at temperatures >1000 K again yields discontinuous films which indicates the metastable character of the ZrO2 films on Pt(1 1 1) substrate.