Structural transformations of zinc oxide layers on Pt(111)

The morphology of ultrathin zinc oxide films grown on Pt(111) was studied as a function of preparation and exposure conditions. The results show that submonolayer films exhibit a large variety of structures that may transform into each other depending on ambient conditions. The transformations are accompanied by substantial mass transport across the surface even at room temperature, indicating the presence and high diffusivity of migrating ZnO_x species. Comparison with other metal-supported ZnO films shows that the metal substrate may play a role in such transformations. The structural diversity of ultrathin ZnO may be responsible for the continuing controversy over the role of ZnO in the catalytic performance of ZnO/metal systems.