Effect Of Proton Irradiation On The Structure And Tribological Properties Of Molybdenum Disulfide Thin Films

The magnetron sputtering MoS₂ films are widely used in the moving components of the spacecraft.However,the research on the influence mechanism of the low-energy proton irradiation on the microstructure of magnetron sputtering MoS₂ film is relatively less.In this paper,the microstructure of magnetron sputtering MoS₂ films were analyzed by means of scanning electron microscopy（SEM）,X ray diffractometer（XRD）,X ray photoelectron spectroscopy（XPS）,transmission electron microscope（TEM）etc.The profilometer and the pin-on-disk friction and wear test machine were used to measure the roughness,friction and wear properties of the films before and after irradiation.The results show that after proton irradiation,a large number of defects are produced in the magnetron sputtering MoS₂ films.With increasing radiation fluence,the ordering degree of the crystal structure in the MoS₂ film decreases gradually,and a large number of vacancies and displacements are produced,which tend to aggregated under irradiation and lead to lattice distortion.In this case,the nanospheres are formed from the curved and contracted crystalline planes.Besides proton radiation has a great influence on the structure of MoS₂ film,it also produces a stronger sputtering effect on MoS₂ surface.The sputtering level increases slightly with the increase of irradiation injection,which makes the surface roughness of MoS₂ changes greatly.After proton irradiation,tribological properties also exhibit regular change.The maximum/average friction coefficient and wear rate of the irradiated MoS₂ thin films are firstly increased and then decreased.Through the analysis and comparison,it is found that the wear is mainly controlled by delamination and adhesion mechanisms under low-fluence proton radiation.The rapid increase of the plastic deformation and the roughness causes the friction coefficient and the wear volume to increase significantly.When the proton fluence reaches higher value,the small delamination mechanism is prevailed during wear process.At the same time,radiation induced refined microstructure and its rolling effect facilitate the reverse material transfer in the friction interface and leads to smooth surface,which is beneficial to reduce wear.