Electronic Noise in Digital and Analog Transition Metal Oxide-Based Memristors

记忆系统目前作为克服计算限制所需的下一代非易失性存储器件而被广泛研究。模拟设备因其模拟突触行为或建立多状态数据存储的能力而受到特别关注。与其他新兴存储器相比，基于过渡金属氧化物的阻性随机存取存储器(RRAM)的独特优势在于其良好的可扩展性、高开关性能以及与互补金属氧化物半导体(CMOS)技术的兼容性。然而，这种设备的可靠性是有限的，部分原因是电子波动可能导致记忆应用中的错误读出，以及突触操作中与阻态加宽相关的不可靠性。这项提议的目的是全面调查三种材料系统中这种波动的性质，即未掺杂和La掺杂的氧化铟和纯氧化钇。在拟议的研究中，将利用缺陷工程技术通过反应分子束外延在功能层中诱导氧空位来生产一系列新的样品。这些材料中的氧缺陷以三种方式产生：(I)氧工程的直接结果，(Ii)通过替代掺杂或(Iii)晶体结构本身产生的结果。制作的样品系列将从材料和结构特性以及在直流和暂态运行条件下的电特性方面进行综合研究。在我们研究的主要部分，我们将使用快速数据采集卡(FDAQ)在整个电流-电压特性范围内进行波动(噪声)光谱测量。此外，我们的目标是开发一种名为连续分析的自动化波动光谱测量方案，用于高通量数据采集和后续处理和分析。我们将把连续分析的框架应用到这三个材料系统中，以获得电阻转换过程中微观输运过程的全面物理图像，最终目标是将材料属性与引起的电子涨落联系起来(噪声工程)。在模拟记忆器件的第一次噪声表征中，我们将特别强调化学计量比的影响，以及在直流和脉冲训练过程中导电细丝稳定的有趣现象。这项拟议工作的影响不仅在于为基础物理学提供有价值的信息，而且还为目标材料的人工突触工程和数据存储应用提供有价值的信息。

Memristive systems are currently intensively researched as the next generation of non-volatile memory devices that are needed to overcome limitations in computing. Special interest is given to analog devices due to their ability to mimic synaptic behaviour or establish multi-state data storage. The particular advantage of transition metal oxide-based resistive random-access memories (RRAM) over other emerging memories lies in their excellent scalability, high switching performance and their compatibility with complementary metal-oxide-semiconductor (CMOS) technology. However, the reliability of such devices is limited partially due to electronic fluctuations that may cause false readouts in memory applications and resistance-state broadening-related unreliability in synaptic operations. The goal of this proposal is to lead a comprehensive investigation on the nature of such fluctuations in three material systems, namely undoped and La-doped hafnium oxide and pure yttrium oxide. Within the proposed research, a novel sample series will be produced utilizing defect-engineering via reactive molecular beam epitaxy to induce oxygen vacancies in the functional layer. Oxygen defects in these materials are created in three ways: (i) as a direct result of oxygen-engineering, (ii) through substitutional doping or (iii) arising intrinsically as a result of the crystal structure. The fabricated sample series will be comprehensively studied in terms of the materials and structural properties, as well as the electrical characteristics under DC and transient operation conditions. In the main part of our investigations we will perform fluctuation (noise) spectroscopy measurements over the whole range of current-voltage characteristics using fast data acquisition cards (FDAQs). Moreover, we aim to develop an automatized fluctuation spectroscopy measurement scheme titled Continuous Analysis for high-throughput data acquisition and subsequent processing and analysis. We will apply the framework of Continuous Analysis to the three material systems in order to attain a comprehensive physical picture of the microscopic transport processes during resistive switching with the final goal of correlating materials properties with the arising electronic fluctuations ('noise engineering'). In this first-time noise characterization of analog memristive devices, we will put special emphasis on the effect of stoichiometry, and also on the intriguing phenomenon of conductive filament stabilization during DC and pulsed training. The impact of the proposed work lies in providing valuable information not only for fundamental physics but also for targeted material's engineering of artificial synapses and data storage applications.