Preparation And Electrical Characteristics Of The Amorphous Carbon Thin Film Synaptic Transistor

In the era of big data,the von Neumann bottleneck has seriously restricted the computer's processing efficiency.In contrast,the human brain has the ability of high efficiency,low power consumption and dealing with complex problems,which is inseparable from the biologic synapse.Therefore,it is of great significance to develop novel electronic devices with synaptic functions for realizing high-performance neuromorphic computing.Because of its extra input,the three-terminal synaptic transistor can realize the separation of read and write operations and the emulation of more synaptic functions,thus being considered as one of the best candidates for artificial synapses.As a kind of carbon material,the tetrahedral amorphous carbon(ta-C)thin film has the advantages of high dielectric constant,high stability,high metal ion diffusion,and simple and controllable preparation process.It is thus highly expected to build the ta-C thin film synaptic transistor with high stability and large-scale integration capability.In this experiment,an electrochemical synaptic transistor based on an tetrahedral amorphous carbon film(ta-C)was prepared,and conducted in-depth research concerning the physical rules and mechanisms of the device's conductance transition and its application for synaptic plasticity simulation.The main works are as follows:First of all,an electrochemical synaptic transistor with an ultra-thin ta-C film as the channel material and solid electrolyte as the gate dielectric was fabricated by the filtered cathodic vacuum arc(FCVA)and ultraviolet(UV)lithography.Secondly,through the constant current charge and discharge test,current-voltage(C-V)oxidation and reduction test,and in situ Raman test,the conductivity regulation mechanism of lithium ion on the ta-C were studied.It was found that under the driving of electric field,lithium ion can react reversibly with sp~2 clusters in ta-C film to generate lithium-carbon compounds,thus changing the carrier concentration and macroscopic conductivity of the film.Finally,by applying pulse voltages to the gate electrode,the effects of pulse voltage parameters on the performance of the ta-C synaptic transistor were systematically studied.Especially,the important synaptic functions like short-term synaptic plasticity(STP),long-term synaptic plasticity(LTP)and spike-rate-dependent plasticity(SRDP)were successfully realized,and the continuous and reversible regulation of multilevel synaptic weight was realized under the condition of low power consumption.At the same time,through the study on ta-C synaptic transistors with different sp~2 cluster contents,it was found that sp~2cluster content of the ta-C film can significantly affect the device's synaptic characteristics.