We report on the direct formation of phase pure nanocrystalline cuprous oxide (Cu 2O) film with band gap ~ 2 eV by microwave plasma oxidation of pulsed dc magnetron sputtered Cu films and the highly controlled oxidation of Cu in to Cu 2O and CuO phases by controlling the plasma exposure time. The structural, morphological and optoelectronic properties of the films were investigated. p-type Cu 2O film with a grain size ~ 20-30 nm, resistivity of ~ 66 Ω cm and a hole concentration of ~ 2 × 10 17 cm - 3 is obtained for a plasma exposure time of 10 min without using any foreign dopants. The optical absorption coefficient (~ 10 5 cm - 1) of the Cu 2O film is also reported. © 2012 Elsevier B.V.