Tantalum oxide films have been prepared by photolysis of Ta(OCP3)(5) vapor under KrF excimer laser irradiation at various laser fluences (50-450 J m(-2)). The composition and stoichiometry of the films were determined by X-ray photoelectron spectroscopy (XPS). The variation of the shape of the Ta 4f XPS peak for surface erosion of samples by argon-ion etching indicated that films were deficient in oxygen atoms compared with the composition of the stoichiometric Ta2O5, though the X-ray diffraction pattern of films obtained at higher laser fluences (more than 300 J m(-2)) corresponded to that of the beta-Ta2O5 phase. The deficiency in oxygen increased with increasing laser fluence to reach the maximum value of about 20% in the laser fluence range 150 J m(-2) to 250 J m(-2) and then decreased. The carbon content in the films was less than the background contamination level (a few %) under the experimental conditions investigated. Various possible reasons for the laser fluence effect on the stoichiometry of films are discussed.