Study On The Surface Physical And Mechanical Properties Of MoS₂ Film Controlled By Light Treatment

Molybdenum disulfide(MoS₂)is a graphene-like layered material.Due to its high carrier mobility,dangling-bond-free surface,adjustable wide band gap and low friction coefficient,MoS₂has wide applications in electronic devices,but with the miniaturization of electronic devices,the specific surface area of MoS₂ films increases,leading to the enhancement of surface effects.Therefore,it is particularly important to explore the applicable law of surface effect at micro scale.In this thesis,MoS₂ thin films have been prepared by chemical vapor deposition(CVD)at 650?for 20 min,1 h,1.5 h and 2 h,and the structure,morphology and properties of the samples were characterized.The main research contents are as follows:(1)The effect of deposition time on MoS₂ film was investigated with Raman spectroscopy,optical microscopy(OM),atomic force microscopy(AFM),Kelvin probe force microscopy(KPFM)and friction microscopy(FFM).The results show that different deposition time has different effects on the morphology,structure,surface potential and surface friction of MoS₂ films.(2)In order to explore the influence of light irradiation and thickness on the surface potential of MoS₂ thin films,the samples deposited for 2 h was illuminated with the white light,and the surface potential was measured by KPFM before and after the light illumination.The results show that the change of surface potential of MoS₂ films induced by the light illumination is dependent on the thickness of MoS₂films,and is irreversible.(3)The samples deposited for 2 h were subjected to light treatment,and AFM,FFM and adhesion test were used to explore the influence of light and thickness on the surface friction of MoS₂ films.The results show that the surface friction of MoS₂films changes under different illumination conditions,which is related to the thickness of MoS₂ film;The change of adhesion force is similar to that of friction force,which indicates that the change of friction force is related to adhesion force.The change of adhesion force mainly results from the electrostatic force due to the variation of the surface potential induced by the illumination changes.Although the change of surface friction force caused by the light illumination is reversible,the change of adhesion is not completely reversible.