Phosphorus doped nanocrystalline NiO thin films were synthesized using radio frequency magnetron sputtering of a prefabricated target on glass and silicon substrates in argon atmosphere. X-ray diffraction studies confirmed the good crystallinity and proper phase formation. Phosphorus doping in NiO films was confirmed from the binding energy determination by X-ray photoelectron spectroscopic studies. Morphological information was obtained from the atomic force microscopic measurement. Determination of band gaps from the UV-vis-NIR spectrophotometric measurement showed that it increased from 3.66 to 3.81 eV corresponding to undoped and 10% P doped NiO thin films. © 2009 Elsevier B.V. All rights reserved.