碲基硫系化合物材料的忆阻特性研究

发布时间：2018-04-25 22:38

本文选题：碲基硫系化合物 + 忆阻器　；参考：《华中科技大学》2014年博士论文

【摘要】：自2008年被实验实现以来,忆阻器就受到了全球研究人员的广泛关注。忆阻器能记忆流经其的电荷,因而在非易失性存储、逻辑运算、神经网络和可编程电路等领域都具有广阔的应用前景。然而目前忆阻器的研究仍处于起步阶段,在材料、器件结构、忆阻机理以及器件电阻的调控上还有许多问题亟需进一步研究。本论文中研究了Ge2Sb2Te5、Ag5In5Sb6oTe3o、Sb2Te3三种不同的碲基硫系化合物材料,制备了忆阻器件,研究了几种不同材料在忆阻特性上的特点,提出了其忆阻机制,探讨碲基硫系化合物忆阻器的器件改进、特性调制方法和可能的应用。本文主要工作与结论如下：首先我们研究了Sb原子含量不超过化学计量比的Ge2Sb2Te5薄膜在非晶态下的忆阻特性,制备了两种Ge2Sb2Te5'忆阻器：一种是基于非活性电极的TiW/Ge2Sb2Te5/TiW结构忆阻器件,高低阻变化范围在1个数量级以内,但器件电阻可多级连续调制,并构建了基于空间电荷限制导电效应的忆阻模型；另一种是采用活性Ag电极的Ta/Ge2Sb2Te5/Ag和Ag/Ge2Sb2Te5/Ag结构忆阻器件,在Ge2Sb2Te5薄膜内部发生Ag导电丝的形成和断裂,导致器件的电阻变化,器件可实现稳定的阻变开关,RoFF/RoN可基本保持在50倍以上,且构建了基于电化学金属化反应的忆阻模型。其次,实验发现AgsIn5Sb60Te30薄膜在非晶态下能够展现出良好的忆阻特性,构建了基于本征的空间电荷限制导电效应和非本征的电化学金属化反应两种忆阻机制的Ag5Iln5Sb60Te30忆阻模型。在由空间电荷限制导电效应和电化学金属化反应共同作用的Ag/Ag5In5Sb6oTe3o/Ag结构忆阻器中,可以实现稳定的电阻渐变调控,精确地对器件电阻进行调制。此外在Ag/Ag5In5Sb6oTe3o/Ag结构忆阻器中,可同时实现双极性和单极性的电阻渐变调制,但双极性的电阻调控所需的脉冲能量比单极性调控更小功耗更低。最后,我们研究了晶态Sb2Te3薄膜的忆阻特性,提出其阻变行为与薄膜内的带电缺陷有关。在高阻态下,由于普尔—法兰克发射效应,器件电阻随外加电压升高而降低；而当外加电压足够大时,Sb2Te3薄膜内的带电缺陷可发生移动,导致器件电阻的进一步突变。当在器件一侧使用活性的Ag电极时,Ag原子退火后会扩散进入Sb2Te3材料,与Te原子结合,在电极/功能层界面附近造成更多的带电缺陷；通过施加合适的脉冲序列,可在Ag/Sb2Te3/Ta忆阻器中同时实现开关切换和电阻渐变调制两种特性。实验发现Ge2Sb2Te5、Ag5In5Sb6oTe3o、Sb2Te3三种碲基硫系化合物均可作为忆阻器件的忆阻材料,其忆阻特性和忆阻机制各不相同。其中使用Ag电极的Ge2Sb2Te5'忆阻器具有最好的开关特性,最适合用于数字应用领域的非易失性存储器和逻辑运算；Ag5InsSb60Te30忆阻器则具有最佳的电阻渐变调控特性,有望用于多值存储和一些模拟应用领域,如模拟神经元突触功能等；Sb2Te3忆阻器同时具备较为稳定的开关特性和电阻渐变调制特性。
[Abstract]:Since the implementation of the experiment in 2008, the memristor has attracted wide attention from researchers around the world. The memristor can memorize its charge, and therefore has a broad application prospect in the fields of non-volatile storage, logic operation, neural network and programmable circuits. However, the research of memristor is still in its infancy, in materials, Device structure, memristor mechanism and device resistance regulation still need to be further studied.
In this paper, three kinds of tellurium based sulfur compounds of Ge2Sb2Te5, Ag5In5Sb6oTe3o, Sb2Te3 are studied. The memristor devices are prepared. The characteristics of the memristor characteristics of several different materials are studied. The memristor mechanism is proposed. The device improvement, the characteristic modulation method and the possible application of the tellurium based sulfur compound memristor are discussed. The work and conclusions are as follows:
First, we studied the memory resistance characteristics of Ge2Sb2Te5 films with Sb atom content not exceeding the stoichiometric ratio. Two kinds of Ge2Sb2Te5'memristors were prepared. One is an TiW/Ge2Sb2Te5/TiW structure recristor based on an inactive electrode. The range of high and low resistance varies within 1 orders of magnitude, but the device resistance can be multistage continuous modulation. A memristor model based on space charge limiting electrical conductivity is constructed, and the other is Ta/Ge2Sb2Te5/Ag and Ag/Ge2Sb2Te5/Ag structure recalling devices using active Ag electrodes. The formation and fracture of Ag conductive wire in the Ge2Sb2Te5 film can lead to the change of the resistance of the device. The device can achieve a stable resistive switch, and RoFF/RoN can be maintained basically. More than 50 times, a memristor model based on electrochemical metallization was built.
Secondly, it is found that the AgsIn5Sb60Te30 film can exhibit good memristor characteristics under the amorphous state. The Ag5Iln5Sb60Te30 memristor model of two kinds of memristor mechanisms based on the intrinsic space charge limiting conductivity and the non intrinsic electrochemical metallization is constructed. In the same Ag/Ag5In5Sb6oTe3o/Ag structure memristor, a stable resistance gradient regulation can be achieved and the device resistance can be modulated accurately. In addition, the resistance gradient modulation of bipolar and unipolar can be realized simultaneously in the Ag/Ag5In5Sb6oTe3o/Ag structure memristor, but the pulse energy required for the bipolar resistance regulation is more than the single polarity modulation. Control smaller power consumption is lower.
Finally, we study the memristor characteristics of the crystalline Sb2Te3 film, and propose that the resistance change is related to the charged defect in the thin film. Under the high resistance state, the device resistance decreases with the increase of the applied voltage, and when the applied voltage is large enough, the charged defect in the Sb2Te3 film can be moved, leading to the device. Further mutation of resistance. When the active Ag electrode is used on the side of the device, the Ag atom will spread into the Sb2Te3 material after annealing and combine with the Te atom to cause more charged defects near the interface of the electrode / functional layer. The switch switch and the resistance gradient can be realized in the Ag/Sb2Te3/Ta memristor by applying the appropriate pulse sequence. Two characteristics are modulated.
It is found that the three tellurium based sulfur compounds of Ge2Sb2Te5, Ag5In5Sb6oTe3o and Sb2Te3 can be used as memristors for memristor devices, and their recristor resistance and memristor mechanisms are different. The Ge2Sb2Te5'memristor using Ag electrode has the best switching characteristics, which is most suitable for non-volatile memory and logic operation in the field of digital use; A The g5InsSb60Te30 memristor has the best resistance gradient regulation and control characteristics. It is expected to be used in multi value storage and some analog applications, such as analog neuron synaptic function. The Sb2Te3 memristor has more stable switching characteristics and resistance gradient modulation characteristics.

【学位授予单位】：华中科技大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM54

【共引文献】