摘要:
忆阻器被定义为第四种基本电子元器件，其模型的研究呈现多样性。目前，忆阻器模型与忆阻器实际特性的切合程度引起了研究者的广泛关注。通过改变离子扩散项，提出了一种新的WOx忆阻器模型，更好地匹配了忆阻器的实际行为特性。首先，新的模型不仅能够描述忆阻器的一般特性，而且能够俘获记忆丢失行为。另外，将新的忆阻器作为神经突触，分析了脉冲速率依赖可塑性、短期可塑性、长期可塑性，并发现了与生物系统中极为相似的“经验学习”现象。最后，考虑到温度与离子扩散系数的关系，探讨了温度对突触权值弛豫过程的影响。实验表明，新忆阻器模型比原来的模型更切合实际，且更适合作为突触而应用到神经形态系统之中。
关键词:
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忆阻器
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离子扩散
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突触可塑性
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温度
Abstract:
Memristor is defined as the fourth basic electronic element, the studies on its models exhibit diversity. Now, the matching extent between memristor model and natural memristor has received researchers’ wide attention. A new memristor model is proposed by changing the ion diffusion term of the WOx memristor, namely, adding another two internal state variables τ and μ which denote the relaxation time and retention, respectively, and the improved model can simulate natural memristor better. Firstly, the new one is able to not only describe the general characteristics of a memrsitor, but also capture the memory loss behavior. In addition, the new memristor can be considered as a neural synapse, under the action of the input pulses with different amplitudes, duration and intervals, the spike rate dependent plasticity, short-term plasticity (STP), and long-term plasticity (LTP) are analyzed, and the “learning experience”phenomenon which is very similar to the biological system is discovered, most of which is due to the back diffusion of the oxygen vacancies during the intervals of the input pulses which are caused by the concentration difference. Moreover, an exponential decay equation is built to describe the relaxation process of STP. Finally, taking into consideration the relationship between temperature and ion diffusion coe?cient, the effect of temperature on the relaxation process of STP is discussed. Experimental results show that the new memristor model can better match the actual behavior characteristics, and more suitably acts as a synapse for being applied to neuromorphic systems.
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