We present an improved preparation method for the growth of high quality crystals of cuprous oxide films grown by thermal oxidation of cupper foils with water vapor. This method proved to be good for preparing cuprous oxide films with high purity and large grain size. X-ray diffraction studies revealed the formation of Cu2O films with preferred (111) orientation. The cuprous oxide diodes fabricated by the above technique have been studied using current-voltage method. (C) 2011 Elsevier B.V. All rights reserved.