Research On Artificial Synapse Based On Physically Transient Self-rectifying Memristor

Electronic synaptic device is the main computing module for hardware based neuromorphic computing.Memristor based artificial synapse become one of the most promising building blocks in efficient neuromorphic computational systems due to ultra-fast switching speed,good scalability,low power consumption,and robust synaptic functions.However,there is serious crosstalk problem in the cross-bar array consisting of physically transient memristor cells,which will not only increase power consumption,but also cause misreading of information.Self-rectifying memristor can well suppress the current crosstalk when the array reads data.It has simple structure and does not require additional selectors,which will increase the memory array integration.On the other hand,physically transient electronics can be degraded under certain conditions after performing their functions.Combining the advantages of both physically transient electronics and memristors,physically transient memristors have great potential for bio-integrated electronics and data security.Therefore,it is essential to develop physically transient self-rectifying memristor.In this paper,the physically transient self-rectifying memory based on Mg O/AZO is studied.The preparation conditions,device structure and thickness of Mg O for the physical transient self-rectifying memory device are studied and the optimal device performance is obtained.The rectification and resistive switching mechanism of self-rectifying memristor are studied,and the synaptic function is simulated by using the adjustable conductivity of the memristor.Finally,the physically transient characteristics of self-rectifying memristor are explored.The specific research contents and results are as follows:(1)The performance of the device is studied from the position and thickness of Mg O and AZO layers and the selection of electrode materials.A Mo/Mg O/AZO/W-structured memristor was obtained using Mo with less antioxidant activity than W as the top electrode.The effect of Mg O and AZO layer thickness on device performance was investigated.By comparison,the device with 5 nm Mg O thickness has the best performance,with a rectification ratio of 10~2 and a durability cycle of 1200 times.Therefore,the optimal structure of the device is Mo/Mg O(5 nm)/AZO(30 nm)/W.(2)The comparison of Au,W and Mo antioxidant metals as top electrodes shows that Mo plays a key role in the resistive switching process of devices.The change of device resistance value is caused by the oxidation of Mo electrodes under electric field to promote the formation of oxygen vacancy conductive filaments.The rectifier performance of the device comes from the potential barrier between Mg O/AZO interface.(3)The synaptic properties and physically transient characteristics of Mo/Mg O/AZO/W self-rectifying memristor were studied.It is proved that the device has multi-level conductance adjustable function,and the LTP and LTD functions of synapses are simulated by continuous pulse excitation.Then the degradation of AZO film in water was characterized by SEM and EDS.The electrical properties of the device disappeared completely after soaking in water for 7 minutes.