To study the effect of Cu doping, In2O3 and Cu-doped In2O3 films were deposited on K9 glass and Si substrates with the same experimental parameters. All the films were found to be body centered cubic and have the same preferred orientation. No secondary phases were detected in Cu-doped In2O3. The atomic ratio of Cu to Cu plus In was approximately 18% in Cu-doped In2O3 films which were found to be n-type. After Cu doping, the resistivity of the films increased by 3 to 4 orders of magnitude and the film with higher Cu content had larger resistivity, due to compensation. Cu doping is found to widen the optical band gap of In2O3 films, possibly due to a metal-insulator transition. (C) 2014 Elsevier B.V. All rights reserved.