Charge Trapping Enabled Memory Properties Of Two-dimensional Photoelectric Materials

The diversity of data types and the explosive growth of data volume put forward higher requirements on the data storage capacity of storage devices.Increasing the integration density of storage devices helps to increase the data storage capacity.However,due to the limitation of basic mechanisms and manufacturing technology,it is difficult to improve the integration of traditional silicon devices.Therefore,it is very important to explore new material systems and physical mechanisms to meet the increasing demand for data capacity.Two-dimensional（2D）layered materials are expected to become the next generation of core semiconductor materials after silicon due to their high integration,excellent electrical conductivity,and flexible tunability.At the same time,2D materials have attracted extensive attention in the field of photoelectric storage due to their characteristics of fast conversion speed,multi-bit data storage,large switching ratio,and low power consumption.The hysteresis effect can be realized through charge trapping.In this paper,the generation mode of charge trapping,the physical mechanism of charge trapping leading to the hysteresis effect,and the memory function of charge trapping are studied.The main research contents are as follows:（1）A novel tin-based 2D perovskite crystal（PEA）₂Cs Sn₂I₇ was prepared,and a 2D perovskite memory device was realized based on the charge trapping of its defect state.Tin-based 2D perovskite（PEA）₂Cs Sn₂I₇with millimeter size,high crystal quality,high phase purity,high electrical conductivity,and excellent photoelectric properties were synthesized by the solution cooling crystallization method.The field-effect hole mobility of tin-based 2D perovskite is as high as 34 cm²·V^-1·s^-1 at 77 K and the photoresponsivity is 1250 A/W at room temperature.At the same time,obvious hysteresis has been observed in the transfer curves of a variety of new tin-based 2D perovskite transistors,and the study of the conductivity at variable temperature indicates that the hysteresis is caused by the charge binding caused by the defect of the sample itself,rather than the ion movement.A 2D perovskite memory device is realized based on the principle that charge trapping can produce hysteresis due to the defect of 2D perovskite.（2）By introducing artificial interface states,controllable hysteresis effects are realized in transition metal dichalcogenides（TMDs）transistors,as well as simultaneous logic and memory functions in a single device.The interfacial states between TMDs and substrate are quantitatively introduced by oxygen plasma treatment,and the charge trapping capacity and hysteresis effect are artificially controlled.The hysteresis effect based on the regulation realizes the 6-bit memory function in the WSe₂ transistors,and the maximum switching ratio can reach 10⁵.The interfacial state regulation method is proved to apply to other TMDs transistors.N-type WS₂ and P-type WSe₂ transistors are integrated on the same silicon chip,and the memory function of the opposite state is realized by artificial interface state control.This integrated TMDs transistors not only achieves low power memory function(operating current is always on the order of 10^-9 A)but also has an inverter logic function.Data operation and storage can be performed on the same integrated unit,reducing the power consumption of data transmission between storage units and logical units,and hopefully breaking the bottleneck of speed mismatch between computing and storage units.（3）Further,based on the principle of interface state charge trapping,the memory function of photoluminescence and Raman optical signal in monolayer WSe₂ are realized.When memory function is realized based on Raman optical signal,the Raman signal intensity switch ratio can reach 10².Finally,the photoluminescence memory function is realized based on the monolayer WSe₂ and 2D perovskite/WSe₂ heterojunction.The memory function of monolayer WSe₂ and heterojunction photoluminescence is complementary.The retention characteristics of the two photoluminescence memories remained unchanged within 60 min,and the durability remained unchanged within 100 cycles,while the light intensity changed opposite under the same input,and the switching ratio was 2.