Scanning tunneling microscopy study on the preparation and characterization of zirconium oxide islands on Ag(100)

We have studied the growth and morphology of Zr oxide films on Ag(1 0 0) by using scanning tunneling microscopy and low-energy electron diffraction. The films have been obtained by reactive deposition of Zr in an O-2 partial pressure of 10(-6) mbar on Ag(1 0 0) in the temperature range between 300 and 570 K without and with subsequent annealing in O-2 atmosphere at temperatures up to 1070 K. The experimental conditions always led to the growth of Zr oxide islands without long-range order, which for a metal coverage of three monolayers of Zr were observed in a mean separation of 20 nm and a height in the order of 1 nm. At large positive sample bias voltages above 3 V the oxide islands appeared as protruding structures. The dependence of the measured height of these islands was found to be consistent with the electronic structure of Zr oxide. In the energy range of the band gap of Zr oxide, the height of the islands appear below that of the Ag substrate which may be explained by the additional tunneling barrier of the oxide. (C) 2002 Elsevier Science B.V. All rights reserved.