CeNx films are prepared by rf ion plating and analyzed by X-ray photoelectron spectroscopy (XPS). Ar/N-2 flow ratios are varied and Ar gas is found to play a very important role in the formation of the stoichiometric CeN film. The shake-up satellite peaks from 4f degrees initial state in the Ce 3d core level vanishes when stoichiometric CeN is formed. The CeN film shows p-type conduction and the room temperature resistivity is 2.1 x 10(2) Omega cm. The optical band gap is 1.76 eV with direct transition, which agrees well with the prediction of Sclar [N. Sclar, J. Appl. Phys. 33 (1962) 2999].