500-nm-thick-CuO:S film has been prepared on a glass substrate by a chemical bath deposition in an aqueous solution containing copper(II) nitrate, ammonium nitrate, and ammonia water at 323-343 K. The CuO:S films possessed a monoclinic lattice and bandgap energy of 1.35 eV, which were characteristic of semiconductor CuO. The deposition mechanism was briefly discussed from the potential-pH diagram thermodynamically calculated for the copper-ammonia-water system. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3530187] All rights reserved.