The chemistry and physics of zinc oxide surfaces

In the present review we will summarize recent experimental and theoretical information which has become available from single crystal studies on ZnO surfaces. While the number of papers dealing with another oxide, rutile TiO2, is significantly larger (although titania does not exhibit a polar surface), also for zinc oxide a basis of experimental and theoretical knowledge as been accumulated, which - at least for the non-polar surfaces - allows to understand physico-chemical processes on an atomic level for an increasing number of cases. In particular with regards to the interaction with hydrogen a number of - often surprising - observations have been reported recently. Some of them carry implications for the behaviour of hydrogen on oxide surfaces in general. We will present the currently available information for both, experiment and theory, and demonstrate the rather large variety of this material's surface properties.