Cu-doped ZnO nano-films were synthesized by a hydrothermal method combined with post-annealing process. The mechanism for the formation of the nano-films can be explained by a Cu-adsorbed face-selective crystal growth inhibition mechanism. The 2 at.% Cu-doped sample behaved p-type conductivity, which can be verified by a p-n homojunction with well-defined rectifying characteristic. The origin of p-type conduction of the Cu-doped sample was studied by XPS and PL analyses. The Cu-Zn(+1) acceptor with the ionization energy of 326 meV should be the main reason for the p-type conductivity. (C) 2015 Elsevier Ltd. All rights reserved.