Transport Modulation Of 2D Semiconductors And Their Electronic Applications

Both logic operation units and memory units based on field effect transistors are the core components of semiconductor devices which promotes the rapid development of modern information technology.Especially,information devices based on novel semiconductor materials have been playing an important role in the application of high-capacity data storage and high-speed data operation.Recently,two-dimensional（2D）semiconductor materials represented by Transition Metal Dichalcogenides have shown great promise in the implementations of next generation semiconductor devices due to the atomically thin thickness and their unique electrical,optical and mechanical properties.Effectively controlled doping engineering of 2D materials appears to be the key to implement the application of logic electronics and memories.Currently,various doping strategies still exist some challenges characterized by non-volatility,controllability,reversibility,stability and spatially selectivity.Besides,designing a multi-value inverter to replace the traditional binary inverter as the basic component of the logic circuit can effectively improve the information density and data operation speed.At the same time,there is insatiable demand of storage technologies to seek further improvements in terms of capacity,speed,retention,and durability.In this thesis,we demonstrate an opto-electrical doping approach that enables precisely controllable modulation of transport properties of 2D materials and their van der Waals heterostructures,and further successfully developed ternary inverter and high-capacity opto-electrical flash memory.In addition,we design van der Waals heterostructure devices taking advantage of 2D materials with unique physical properties,to achieve floating-gate flash memory with fast speed and high capacity.The main topics of this thesis are listed as follows:1.We demonstrated an opto-electrical doping approach through the combination of electrostatic gating and ultraviolet（UV）light illumination that enables highly effective,nonvolatile,reversible,stable,ultrafast,and spatially selective doping of MoTe₂ transistors.The doping scheme can achieve unipolar n-type and p-type MoTe₂transistor with high carrier mobility and concentration.Besides,the doped MoTe₂transistors can work stably in ambient air with negligible degradation and hysteresis.2.We implemented a ternary inverter based on the single anti-ambipolar transistor which formed by MoTe₂/MoS₂ heterostructure through opto-electrical doping approach.3.Taking advantage of the non-volatility,controllability and reversibility of opto-electrical doping,different levels of doping are implemented for MoTe₂ as different storage states,thus,we developed a high-capacity 3-bit flash memory.4.We demonstrated floating-gate MoTe₂ flash memory based on graphene/h-BN/MoTe₂ heterostructures,which is capable to store multi-bit per cell by programming/erasing with different gate pulse.Furthermore,the MoTe₂ flash memory also shows 1μs switch speed with excellent retention and endurance properties.5.We further developed floating-gate ReS₂ flash memory device.Taking advantage of anisotropic electrical properties of ReS₂,the ReS₂ memory can achieve direction-sensitive multi-level data storage programmed/erased by single gate pulse.Besides,the ReS₂ flash memory shows 1μs switch speed with excellent retention and endurance properties.