The chemical formation of a ZnO layer on gold substrates in an aqueous solution containing Zn(NO3)(2) and dimethylamineborane was investigated in situ using an electrochemical quartz crystal microbalance (QCM). The initial growth rate of ZnO increased with the increase in the initial concentration of oxygen dissolved in the solution, while the presence of nitrate ions is also required for the growth of ZnO; the use of sulfate ions instead of nitrate ions as a counteranion did not allow the formation of a ZnO layer. Agitation or intensive aeration of the solution had no obvious effect on the ZnO growth, suggesting that the dissolved oxygen works only in the initial stage of growth. The growth of the layer occurred at any temperature of the solution in the range of 298 to 338 K, but the crystallinity of the layer increased with the increasing temperature. (c) 2006 The Electrochemical Society.