The Study Of The Pulsed Laser-induced Synthesis Of MoS₂ Films

Molybdenum disulfide(MoS₂),as a transition metal sulfide,has become a hot material in the post-silicon era due to its excellent properties in electrical,optical,and mechanical properties.Unlike the zero band gap of graphene materials,when MoS₂transforms from multiple layers to a single layer,its energy band changes from indirect band gap to direct band gap with band gap of 1.8e V.In addition to excellent photoelectric performance,MoS₂ film has great potential in microelectronic device applications.In this research,the electronic structure and system stability of intrinsic MoS₂ and Au,Pt,Pd doped monolayer MoS₂ were studied based on first principles using Materials Studio(MS)software.The calculation results show that the intrinsic MoS₂ is a direct bandgap semiconductor with a band gap of 1.74 e V.All three doping systems can exist stably and the band structure moves to the low energy direction,as well as impurity bands appear in the forbidden band.The MoS₂ film was synthesized by pulsed laser method with MoCl₅ and thiourea as molybdenum source and sulfur source.The MoS₂ films were characterized by optical microscope,Raman,AFM,HRTEM,SAED and XPS.The results show that a large-area continuous MoS₂ film with both 1T and 2H phase is synthesized,and the thickness of the film can be controlled by changing the concentration of MoCl₅.The synthesis of MoS₂ thin films and the doping with Au,Pt and Pd elements were carried out in one step by pulsed laser method using chloroauric acid,platinum chloride and palladium chloride as dopants.The XPS,EDS,STEM and TEM methods were used to verify that the three doping systems successfully incorporated doping elements into MoS₂.Field effect transistors of undoped MoS₂ and Au doped MoS₂ were designed and fabricated.The result of transfer characteristic curves shows that the Au-doped MoS₂field-effect transistor transforms from n-type to p-type,the on/off current ratio is 10⁵,the carrier mobility is 0.57 cm²V^-1s^-1,the subthreshold swing is 0.66 V/dec,and the threshold voltage is-13.13V.It is confirmed that the doping of Au to MoS₂ is p-type doping.