过渡族金属氧化物中电阻开关特性的研究

项目名称： 过渡族金属氧化物中电阻开关特性的研究

项目编号： No.10804048

项目类型： 青年科学基金项目

立项/批准年度： 2009

项目学科： 生物科学

项目作者： 夏奕东

作者单位： 南京大学

项目金额： 24万元

中文摘要： 氧化物的电阻开关特性可分为单极型和双极型两类，这两类效应具有截然不同的开关特征与机理。在本项目中，我们围绕单极型和双极型的物理机制，以几类材料（如LaLuO3、LiNbO3、GaOx）为代表，分别开展针对性的研究。我们的研究表明，在单极型开关特性中，氧空位的作用机制是体效应机制。我们采用CBH理论，研究了阻变过程中材料内相互关联的缺陷之间的势垒随缺陷间位置变化的物理规律，分析了非晶态材料中导电网络的联结与切断的物理过程。而双极型开关特性主要表现为一种界面控制机制。因此，我们重点研究了电极/氧化物界面微结构、界面反应以及界面势垒。电极材料的种类极大程度地影响着双极型开关行为。器件的开关方向与电极材料选择密切相关。选用Pt电极时，Pt/氧化物界面势垒起主导作用。我们采用Richardson方法获得了界面势垒高度。选用Ag、Ti等反应电极，则能够在氧化物材料中实现由氧化还原反应控制的双极型开关。另外，由于双极型开关其本质是一种忆阻特性。在本项目中，我们发展了一种基于铁电二极管的忆阻器，该器件能够实现仿生物突触的长时程增强效应。在上述研究基础上，我们制备了crossbar结构的阻性存储阵列。

中文关键词： 单极型；双极型；氧空位；correlated barrier hopping理论；界面控制机制；电极/氧化物薄膜界面

英文摘要： There are two schemes with respect to the electrical polarity required for the resistive switching in oxides, unipolar and bipolar, which show distinct switching characteristics. In this project, we studied the different roles of oxygen vacancies in unipolar and bipolar switching, respectively. We reported that the unipolar switching is determined by bulk effect. The transition between high and low resistance states is attributed to the change in the separation between oxygen vacancy sites in the light of the correlated barrier hopping (CBH) theory. The CBH theory can provide the basic principle for understanding the percolation mechanism in the unipolar switching. In bipolar switching, the switching is dominated by the interface effect. According to this principle, we focused on the microstructure of electrode/oxide interface, interface reaction, interface barrier, and their impact on the bipolar switching as well. We reported that the switching direction depends on the electrode materials. In the device consisting of Pt electrode, the Schottky barrier at Pt/oxide interface mainly determines the variation in conduction. By using the Richardson's method, the Schottky barrier height can be obtained. If Pt is replaced by Ti as the electrode, the switching polarity changes from "counter-Figure-8" to "Figure-8." We also found that when Ag and Ti are employed as the reactive electrode, the devices work in a way controlled by the electrically-derived redox. In addition, the bipolar switching is in general a kind of memristive switching. In this project, we also developed a kind of memristive device composed of ferroelectric diode. Such device can achieve the synaptic learning abilities. Finally, we fabricated some crossbar memory array based on the above researches.

英文关键词： unipolar switching; bipolar switching; correlated barrier hopping theory; interface-limited mechanism; electrode/oxide interface