Ethanol is used as a precursor during the growth of zinc oxide (ZnO) by low-pressure chemical vapor deposition (LPCVD). By adding ethanol, the surface of the deposited ZnO layer is flattened and its roughness is decreased about sevenfold. The layers become increasingly stressed and their resistivity grows significantly. We propose an explanation for the observed behavior based on the catalytic decomposition of ethanol at the ZnO surface and on the growth of selected crystal planes. By using ethanol for the last 10% of the total ZnO layer growth only, sheet resistance is maintained and roughness is slightly decreased. Our results indicate that such LPCVD ZnO bilayers could be a promising method to modify the ZnO surface morphology before cell deposition, thus, providing an alternative to argon plasma treatment, which is typically reported to improve solar cell parameters such as open-circuit voltage and fill factor. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4775483]