Reactivity of ZnO: Impact of polarity and nanostructure

The effects of atomic hydrogen and nitrogen produced by remote r.f. H2 and N2 plasmas on the structure, morphology, and optical and electrical properties of Zn- and O-polar ZnO crystals and on ZnO thin films grown by metal-organic chemical vapour deposition (MOCVD) have been studied. It is found that the Zn-polar form is highly reactive with atomic hydrogen, while the O-polar form is almost inert. This difference in reactivity allows one to discern the O-polarity of the (0001) oriented ZnO thin films grown by MOCVD. A decrease of the resistivity of the grain-like MOCVD films is found upon atomic hydrogen treatment. Conversely, atomic nitrogen treatment results in p-type doping of the ZnO film and in an improvement of the surface morphology and microstructure.