The Study On The Contact Characteristics Between Metal And MoS₂ Films

Due to its excellent physical and chemical properties,two-dimensional layered transition metal dichalcogenides have great potential for applications in optoelectronic devices and biosensors.MoS2 is a layered semiconductor material dependent on thickness with adjustable band gap,large specific surface area,good mechanical flexibility,high thermal stability and excellent photoelectric properties.These characteristics present broad application prospects in field effect transistors,sensors,catalysts and other fields.However,the preparation of large-area,high-quality molybdenum disulfide film remains to be solved,and the contact properties with metal have become a bottleneck restricting their development.Therefore,it is of great significance to optimize the preparation process of molybdenum disulfide and investigate its contact characteristics with metals.In this paper,the preparation of monolayer and multilayer MoS2 thin films was studied.The thin film samples were characterized and analyzed by means of optical microscopy,atomic force microscopy,Raman and photoluminescence.Subsequently,four electrodes of aluminum,nickel,copper and iron were prepared and their contact characteristics were studied.The main conclusions are as follows:1.Monolayer and multilayer MoS2 thin films were successfully prepared on sapphire(Al2O3)substrates by quasi-closed crucible CVD.When the growth temperature is 850℃ with the growth time of 20min,the morphology of the prepared MoS2 domains is continuous film with a distance of 13cm between MoO3 and substrate.While a single-layer MoS2 thin film is obtained when the substrate is placed inside the quasi-closed crucible,and multilayer MoS2 film can be obtained on the cover of the crucible2.The contact characteristics of four metals,aluminum,nickel,copper and iron,were analyzed.The results show that Al forms a Schottky contact with the MoS2 film at room temperature and presents ohmic characteristic after RTP.While Ni,Cu and Fe express an ohmic contact at room temperature.The contact resistance between the same kind of metal and the multilayer MoS2 film is smaller than the monolayer MoS2.Especially,the contact resistance of Ni and multilayers MoS2 film reaches a minimum value of 4.497Ω·cm.And thus,the contact resistance of Ni-MoS2 significantly decreases from 4.497 Ω · cm to 1.07 Ω· cm after RTP.resistance of Ni-MoS2 significantly decreases from 4.497 Ω·cm t0 1.07 Ω·cm after RTP.3.The transport of carriers and the change of contact resistance with temperature were systematically investigated by testing the Ⅰ-Ⅴ characteristics under high and low temperature conditions.The analysis shows that the carrier transport mechanism is hot electron emission and the contact resistance increases with the increase of temperature.