Carbon films were deposited by sputtering a graphite target with Xe+ ion beam. During deposition, an additional low-energy ion beam, composed of O+ ions and Ar+ ions, was irradiated on the growing layers. The resistivity of the films was found to decrease with increasing relative concentrations of O+ ions against Ar+ ions and against carbon atoms. It was also found that scarce oxygen atoms were observed in the films by irradiating O+ ions. The variable hopping conduction model was found to be applicable to describe the temperature dependence of the film resistivity for all specimens studied with temperatures of two; i.e. lower than 50 K and higher than 50 K. Furthermore, density of hopping sites increased with increasing relative concentration of O+ ions. Some discussions such as mechanism of hopping sites in the film and work of oxygen during deposition were also expressed.