Research On Growth Of Monocrystal-MoS₂ Films And Regulation Mechanism Of Its Synaptic Device

The 21st century is an information age with explosive growth of data.Almost a hundred exabytes of data are transmitted and stored every day.Due to the existence of"storage wall",the traditional von Neumann architecture cannot process amounts of data quickly and efficiently,which limits the development of technology such as artificial intelligence,big data,and the Internet of things.Therefore,it is necessary to solve the problem by breaking the traditional computer architecture at the hardware level.The emergence of neuromorphic computing architecture with characteristics of storage and calculation integration,high parallelism has achieved a revolutionary breakthrough,becoming a research hotspot.Recent researches have shown that synaptic transistors based on two-dimensional materials have great advantages and potential in simulating neural synapses and building neural networks.However,the practical applications of MoS₂ synaptic transistors mainly solve the following problems.The one is the controllable preparation and mechanism of large-scale and high-quality MoS₂ domains,and another is the synaptic performance and mechanism of MoS₂ transistors.The paper will explore the following two points:1.Exploring the large-size growth of monocrystal-MoS₂ and its growth mechanism.The chemical vapor deposition（CVD）method was used to explore the influence of growth temperature on the size of MoS₂ films.The triangle side length of119.2μm single-crystal MoS₂ film was achieved at 820℃.The growth mechanism was analyzed by constructing a Mo O₃ concentration gradient curve.The results demonstrate that Mo O₃ concentration is a key factor to affect the size of MoS₂ films.The conclusion provides theoretical guidance for the controllable growth on the film size.Then the quality of MoS₂ films is characterized by Raman,AFM,XPS,HRTEM and others.The peak difference of Raman is 18.84 cm^-1 and the film thickness is 0.67nm.These results indicate that the sample is single layer.HRTEM and SADE demonstrate that the sample is single-crystal.This work lays the material foundation for the next step in building high-performance synaptic transistors.2.Investigation on the synaptic performance and regulation mechanisms of MoS₂ transistor.The back-gated FETs based on the as-grown MoS₂ films were fabricated by traditional micro-nano processing technology,then the synaptic properties and regulation mechanisms are systematically studied.The research demonstrates that MoS₂ exhibited excellent synaptic performance when the drain-terminal and gate-terminal are used when as the input terminal.The device realizesexcitatory/inhibitorypostsynapticcurrent（EPSC/IPSC）,spike-amplitude-dependent plasticity（SADP）,spike-timing-dependent plasticity（STDP）,and long-term plasticity（LTP）of biological synapses,which breaks through the fixed thinking of artificial synaptic devices with a single input.The conductance modulation of drain-and gate-terminal can attribute to the migration and charges trapping/de-trapping process of sulfur vacancies.By employing monocrystalline-MoS₂ films,the device not only attains a much lower operation voltage（2 V）and a higher endurance（5000 cycles）but also can be programmed by low energy consumption（～3.75 p J）with gate-terminal,indicating practical value and great potential of complex neuromorphic application.