Optoelectrical Properties And Applications Study Of Two Dimensional Layered Semiconductors Based Devices

In recent decades,the innovation of semiconductor manufacturing technology and the development of very large scale integration?VLSI?promote the progress of the semiconductor industry.Following the Moore's Law,the amount of the devices on a chip are increasing,as well as improving the performance and reducing the cost.However,the chanllenge of severe short channel effect?SCE?cannot be avoided when the feather length is reduced below 10 nm,such as large leakage current or bad gating control ability.In term of above,on the one hand,we need to optimize the configurations to decrease the parasitic device capacitance or SCEs,such as the proposal of Fin field effect transistor?FinFET?and silicon on insulator?SOI?.On the other hand,it is desirable to search for suitable semiconductor marterials to replace the commercial silicon based materials.In particular,diverse layered two-dimensional?2D?materials with tunable bandgaps and excellent carriers transport behavior have exhibited extraordinary electrical and optical properties in logic circuits,photodetectors,light-emitting diodes,and energy storages devices,which have demonstrated that layered 2D matierals possess intrinsically advantages in next-generation of advanced optoelectronic devices.Therefore,our main research focus on the fabrication,characterization,and applications of layered InSe and MoS₂,including the following works.?1?High mobilies in Layered InSe transistors with superior stability have been demonstrated by indium encapsulation induced surface charge doping method?w/In InSe FET?,as well as the ideal operations of logic gates.Tunability and stability in the electrical properties of 2D semiconductors pave the way for their practical applications in logic devices.In our work,a robust layered InSe field-effect transistor with tunable doping behavior,as well as superior controlled stability,is demonstrated by depositing an indium?In?doping layer.The optimized w/In InSe FET delivers a high electron mobility up to 3700 cm² V^-1 s^-1 at room temperature,which can be retained for about 2 month.Further insight into the evolution of the position of the Fermi level as well as the microscopic device structure with different In thicknesses demonstrate the optimum electron-doping behavior and stability at the 32 nm In/InSe interface.Furthermore,not only the carrier transport behavior but also the contact resistances are improved through the In insertion between InSe and Au electrodes.Based on the above,the flexible functionalities of the logic-circuit applications,for instance,inverter and NAND/NOR gates,are realized with these low-consumption surface-doping InSe FETs?32 nm_In?,which exhibit the promising use of 2D-based materials in electronic devices.?2?Low-power consuming and high sensitive tactile switch based on 2D layered InSe tribotronic has been successfully developed by coupling a w/In InSe FET and a triboelectric nanogenerator?TENG?.The development of diverse artificial intelligence and smart interface systems is propelling current technology.However,these portable electronics consume plenty of power every day,which lead to worse energy shortages.It is important to establish a way to convert energy from scavenging mechanical stimulation to power nanoscale electronics to meet market demands.In this regard,an InSe tribotronic transistor?denoted as w/In InSe T-FET?obtained through the vertical combination of an In-doped InSe transistor?w/In InSe FET?and triboelectric nanogenerator is demonstrated.By adjusting the distance between two triboelectrification layers to modulate the induced charges,a negative electrostatic potential can be generated,which could serve as a gate voltage to tune the charge carrier transport behavior of the InSe channel.Benefiting from the surface charging doping of the In layer,the w/In InSe T-FET exhibits high reliability after 500 cycles and sensitivity with a large on/off current modulation of 10⁶ under a low drain–source voltage of 0.1 V and external frictional force.To demonstrate its function as a power-saving tactile sensor,the w/In InSe T-FET is used to sense‘INSE'in Morse code and power on a light-emitting diode without the external gate bias,which reveals the promise of InSe tribotronic transistor for use in nanosensors with low power consumption as well as in human interfacing systems.?3?The Bi₂S₃@MoS₂ composite was demonstrated by two–step hydrothermal method.The experimental and theoretical results indicate that the enhanced photogenerated carriers transfer behavior would lead to a proming application of photodetector devices.Fantastic heterostructure is known as its enhanced light-harvesting capacity and effective separation of photogenerated carries,which earns much attention for potential use in photodetectors and photocatalysis.Thus,a 3D dandelion-shaped Bi₂S₃@MoS₂ microsphere heterostructure has been successfully fabricated by simple hydrothermal method,in which MoS₂ nanosheets,as the wings,compactly decorate the Bi₂S₃ nanorods.Based on the theoretical results of band structure,the staggered type II band alignment between MoS₂ and Bi₂S₃ allows the charge transfer from the conduction band of Bi₂S₃ to that of MoS₂,which can effectively improve the separation,restain the recombination,and prolong the lifetime of the photogenerated carrier.The research results reveal that the Bi₂S₃@MoS₂ based photodetector exhibited enhanced photoconductance and phohtoresponse under the illumination of visible light.Besdies,compared with pure MoS₂ or Bi₂S₃,Bi₂S₃@MoS₂ composite delivered improved visible light photocatalytic efficiency of 92%and cycling stability for the degradation of organic dyestuffs,which could be contributed to the more active sites and higher light utilization.?4?C@MoS₂-SnO₂@Gr nano-composite has been fabricated by one-step hydrothermal methods and its energy storage application as an anode for Li⁺battery has been systematically studied.With high specific capacity,excellent rate capability,and recyclability,lithium ion batteries?LIBs?become one of the most important energy storage systems due to the worse energy shortages.Known as the high specific capacity,2D materials-based anode materials are regarded as one of the ideal candidates.Thus,we prepared the C@MoS₂-SnO₂@Gr composite by one-step In situ hydrothermal method.In this composite,the synergistic effects between MoS₂-SnO₂ benefit the charge transfer kinetics.In addition,the ultrathin?2 nm?carbon layer and graphene matrix offer a bi-continuous conductive path for effective ion/electron transport.Based on the investigation of microstructure and theory analysis,the ameliorated electric contact between MoS₂ and SnO₂ can promote the extraction of Li⁺,successively improve the reversible reaction.The research results indicate that the energy storage process of C@MoS₂-SnO₂@Gr anode is dominated by the surface capacitve kenitics,which leads to a high capacity of 680 at 2.5 A g^-1 after 2000 cycles.Therefore,it could conclude that the excellent rate performance and cycling stability obtained from C@MoS₂-SnO₂@Gr anode establish a paradigam for the applications of 2D composite material anodes in energy storage devices.