Reactivity of ZnO: Impact of polarity and nanostructure

The effects of atomic hydrogen and nitrogen produced by remote r.f. H-2 and N-2 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.