Research On The Controllable Preparation And Performance Of MoS₂ And Carbon Nanoparticle/MoS₂ Composite Films

Molybdenum disulfide（Mo S₂）is one of the most extensively studied two-dimensional semiconductor materials,with its direct bandgap structure considered to have significant advantages in optoelectronic device applications.However,large-area Mo S₂films prepared currently often suffer from sulfur vacancy defects（SVs）,which can form charged excitons with excitons and reduce the probability of photogenerated electron-hole recombination,thereby affecting the optoelectronic performance.Therefore,developing a growth method to reduce SVs defects is of great significance for the practical application of Mo S₂films.On the other hand,conductive carbon-based composite Mo S₂materials have attracted attention for modulating the performance of Mo S₂and expanding its application range,as conductive carbon-based materials（such as graphene,carbon nanotubes,carbon dots,etc.）can effectively promote the separation and transfer of photogenerated charges in Mo S₂under light illumination,as well as participate in redox reactions on the active sites of the two-dimensional structure.In this thesis,on the one hand,a novel sodium-calcium glass-assisted method is proposed to achieve controllable preparation of high-quality centimeter-scale Mo S₂films on Si O₂/Si substrates.First,sulfur and molybdenum pentachloride react inside the molten sodium-calcium glass to form Mo S₂molecules,and the presence of Na ions effectively lowers the formation barrier of Mo S₂,thereby suppressing the formation of SVs.Then,Mo S₂molecules diffuse to the surface of the molten glass,and finally,the continuous film is deposited on the downstream Si O₂/Si substrate by the carrier.Compared with the conventional preparation of single-layer Mo S₂films,the fluorescence peak intensity is increased by 5906%.In addition,compared with Na Cl powder-assisted growth,the Na ions in this process only play a catalytic role and do not form Na₂S particles,so the surface of the obtained Mo S₂film is very clean.On the other hand,carbon nanocomposite particles（CNPs）were successfully deposited on Mo S₂films using a two-step method,realizing controllable preparation of centimeter-scale CNP/Mo S₂films.On the basis of constructing field-effect transistors,the electrical properties of CNP/Mo S₂films were studied.The results show that the conductivity of CNP/Mo S₂films is significantly better than that of Mo S₂films,and the device conductivity is increased by 5 orders of magnitude（zero gate voltage）.Meanwhile,unlike Mo S₂’s typical n-type semiconductor properties,CNP exhibits typical semimetallic properties.The conductivity mechanism of CNP/Mo S₂films can be understood as the Schottky barrier formed between conductive CNPs and Mo S₂.As the temperature increases,more electrons flow from Mo S₂to CNPs,and then transfer between different CNPs on the Mo S₂film in a nearest-neighbor hopping mode.In addition,CNP/Mo S₂has a good temperature coefficient of resistance,with a value of-0.0052 K^-1at 280 K,which is comparable to that of common metals,and it is expected to be applied in infrared detection,temperature sensing,and electrochemical devices.