Research On STDP Characteristics Of LiNbO₃ Single Crystal Thin Film Memristor

Due to the advantages of simple structure,parallel processing,and breakthrough of von Leuman's bottleneck,the memristor has great potential in building a brain-like neuromorphic computing system.The single crystal material has fewer defects and good uniformity,which provides an ideal platform for ion migration.Memristors based on the oxygen vacancy transfer mechanism can exhibit better multi-resistance characteristics,can simulate STDP rules,and are more suitable for building large-scale brain-like systems.However,there are relatively few studies on single crystal thin film memristors,and there is a lack of discussion on the relationship between materials and STDP characteristics.Therefore,exploring the relationship between single crystal materials and device STDP characteristics is of great significance for preparing brain-like chips and building a new generation of computer systems.In this paper,lithium niobate single crystal thin film memristors with good STDP characteristics were prepared based on lithium niobate single crystal thin films using argon ion etching and oxygen annealing.The relationship provides a good synaptic device for the construction of brain-like systems.The specific work and conclusions of this article are as follows:1.Control the etching time of argon ions for lithium niobate single crystal thin film,respectively,and prepare single crystal thin film memristors with thickness of 350 nm,300 nm,250 nm and 200 nm.Through the test of the tunnel scanning microscope,it is known that the thickness of the lithium niobate is well controlled;the test results of the atomic force microscope show that the etched surface is smooth and uniform;the measurement results of the electron paramagnetic resonance instrument show that the etching is accompanied by the introduction of oxygen vacancies.After the electrical performance test,the device's electrical-forming-voltage decreased from 24 V to 9 V,which indicating that the electrical formation voltage decreased significantly;the excessive oxygen vacancy introduced by the etching for a long time leads to the deterioration of the data retention characteristics,anti-fatigue characteristics and switching ratio,making The device is not suitable for the construction of brain-like neuromorphic computing systems.2.Adopt oxygen annealing to reduce the excessive oxygen vacancy introduced by etching.After testing,oxygen annealing has no effect on the thickness of the material,the roughness of the etched surface is slightly improved,and the oxygen vacancy on the surface is significantly reduced.The electrical performance test results show that the switching ratio of the device is significantly improved,the data retention characteristics and the fatigue resistance characteristics are significantly optimized,and the multiresistance state of the device is more prominent.Based on the optimized device,the brain characteristics such as PPF,PTP and forgetting curve are simulated,and the result proves that the device has the potential to be used in the hardware of brain-like neuromorphic computing systems.3.Based on the optimized device,the STDP characteristics of the device were studied by changing the electrical pulse stimulation parameters.The STDP characteristic is essentially the multi-resistance state of the device in the brain-like system,that is:the appropriate oxygen vacancy concentration makes the multi-resistance state of the device more obvious,and exhibits better STDP characteristics and the learning window is adjustable.Therefore,on the memristor based on the oxygen vacancy migration mechanism,the appropriate oxygen vacancy concentration is the key to the preparation of brain-like chips.