 MoS 2 -Ag composite film was co-deposited by rf-sputtering technology and irradiated by atomic oxygen (AO) using a ground AO simulation facility. The structure, morphology, composition and tribological property of the composite films before and after the AO irradiation were investigated using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), X-ray photoelectron spectroscope (XPS) and ball-on-disk tribometer, respectively. The results revealed that the MoS 2 -Ag

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... osite film was severely oxidized by the AO irradiation and the wear resistance was declined significantly; the MoS 2 phase was mainly oxidized to MoO 3 and the Ag was changed to a mixture of AgO and Ag 2 O; and the cracking phenomenon was obvious after the AO irradiation. The oxidation behavior was mainly controlled by the Ag, not the MoS 2 .