An contacts were deposited on bulk, n-type single-crystal ZnO at either 77 K or 300 K. The room temperature deposition produced contacts with ohmic characteristics. By sharp contrast, the cryogenic deposition produced rectifying characteristics with barrier heights around 0.4 eV. The differences in contact behavior were stable to anneal temperatures of similar to 300 degrees C. There were no differences in near-surface stoichiometry for the different deposition temperatures, while the low temperature contacts showed a more uniform appearance. With further optimization of the predeposition cleaning process, this may be a useful method for engineering barrier heights on ZnO. (c) 2006 Elsevier B.V. All rights reserved.