硫系化合物电子突触器件测试方法研究

发布时间：2019-05-21 18:58

【摘要】：当今以密度驱动发展的存储器技术发展逐渐达到其物理极限，功能驱动的认知存储器件可能成为延续摩尔定律的接班人。本文首先把认知存储器和当前主流存储器作比较，阐述了认知存储器的优点。电子突触器件作为一种重要的认知存储器件，近几年受到国内外研究人员的广泛关注。这样一种器件既能够实现数据存储，还能够模拟生物神经元突触的一些认知功能，为认知计算奠定了器件基础。本文介绍了生物神经突触电特性的一些基本概念和理论，并基于此提出了在电子突触器件中实现生物神经元突触特性及功能的一些条件和要求。生物神经元突触的最基本和重要特性是突触可塑性，突触的权重即神经元之间的连接强度能够在生物电信号刺激下增加或减小。为在电子突触器件中模拟突触可塑性，要求器件能够在施加的电信号作用下，实现电阻值的渐变。本文采用硫系化合物材料，可基于其具有的两种不同电特性进行阻值调制：相变特性和忆阻特性。（1）硫系化合物可在晶态和非晶态之间可逆转换。在非晶向晶态转变的晶化过程中存在包括成核和生长两个过程，随施加电脉冲而所积累能量的增加，晶化程度上升，直到完全晶化成为多晶，调节晶化程度能调节材料电阻。（2）硫系化合物材料存在能捕获释放载流子的缺陷，以及作为银等活泼小半径金属离子的固态电解质，具有忆阻特性，能通过控制电流方向改变电阻大小。根据硫系化合物的两种阻变机理，以及所要实现的神经突触功能的特点，提出一套针对利用阻变器件实现神经突触功能的测试方法，包括：直流测试、简单脉冲测试、设计突触前后刺激脉冲以及电子突触功能实现。构建所需测试平台，，能提供两通道脉冲信号以及采集反馈信号。测试了以GeSbTe和AgInSbTe为功能材料的两种电子突触，并成功实现了神经突触功能，具体为活动时序依赖突触可塑性。
[Abstract]:Nowadays, the development of density-driven memory technology has gradually reached its physical limit, and functional-driven cognitive memory devices may become successors to Moore's law. In this paper, the advantages of cognitive memory are described by comparing cognitive memory with current mainstream memory. As an important cognitive memory device, electronic synaptic devices have been widely concerned by researchers at home and abroad in recent years. Such a device can not only realize data storage, but also simulate some cognitive functions of biological neuron synapses, which lays a device foundation for cognitive computing. In this paper, some basic concepts and theories of synaptic characteristics of biological neurons are introduced, and some conditions and requirements for realizing synaptic characteristics and functions of biological neurons in electronic synaptic devices are put forward. The most basic and important characteristic of synapses in biological neurons is synaptic plasticity. The weight of synapses, that is, the connection intensity between neurons, can be increased or decreased under the stimulation of bioelectrical signals. In order to simulate synaptic plasticity in electronic synaptic devices, the device is required to realize the gradual change of resistance under the action of applied electrical signals. In this paper, sulfur compounds can be used to modulate the resistance values based on two different electrical properties: phase transition characteristics and memristor properties. (1) sulfur compounds can be inversely converted between crystalline and amorphous states. There are two processes in the crystallization process from amorphous to crystalline, including nucleation and growth. With the increase of energy accumulated by applied electric pulse, the degree of crystallization increases until the complete crystallization becomes polycrystal. Adjusting the degree of crystallization can adjust the resistance of the material. (2) Sulphur compound materials have defects that can capture and release carriers, as well as solid electrolytes as active and small radius metal ions such as silver, which have the characteristics of memristor. The resistance can be changed by controlling the direction of the current. According to the two resistance mechanisms of sulfur compounds and the characteristics of synaptic function to be realized, a set of test methods for realizing synaptic function by using resistive devices are proposed, including DC test, simple pulse test, The design of presynaptic stimulation pulse and the realization of electronic synaptic function. The required test platform can provide two-channel pulse signal and collect feedback signal. Two kinds of electronic synapses using GeSbTe and AgInSbTe as functional materials were tested, and the synaptic function was successfully realized, which was called active sequence dependent synaptic plasticity.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TP333

【共引文献】