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

忆阻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设备而被深入研究。特别感兴趣的是模拟设备，由于其模仿突触行为或建立多状态数据存储的能力。基于过渡金属氧化物的电阻式随机存取存储器（RRAM）相对于其他新兴存储器的特殊优势在于其优异的可扩展性、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，这种器件的可靠性部分地由于电子波动而受到限制，电子波动可能导致存储器应用中的错误读出和突触操作中的电阻状态加宽相关的不可靠性。该提案的目标是对三种材料系统（即未掺杂和掺杂镧的氧化铪和纯氧化钇）中这种波动的性质进行全面调查。在拟议的研究中，一种新的样品系列将通过反应分子束外延利用缺陷工程来诱导功能层中的氧空位。这些材料中的氧缺陷以三种方式产生：（i）作为氧工程的直接结果，（ii）通过替代掺杂或（iii）作为晶体结构的结果内在地产生。所制造的样品系列将在材料和结构性能方面进行全面研究，以及在直流和瞬态操作条件下的电气特性。在我们调查的主要部分，我们将使用快速数据采集卡（FDAQs）在整个范围内的电流-电压特性进行波动（噪声）光谱测量。此外，我们的目标是开发一个自动化的波动光谱测量方案，题为连续分析的高通量数据采集和后续处理和分析。我们将连续分析的框架应用于三种材料系统，以获得电阻开关过程中微观传输过程的全面物理图像，最终目标是将材料特性与所产生的电子波动（“噪声工程”）相关联。在模拟忆阻器件的首次噪声表征中，我们将特别强调化学计量的影响，以及直流和脉冲训练期间导电细丝稳定的有趣现象。所提出的工作的影响在于，不仅为基础物理学，而且为人工突触和数据存储应用的靶向材料工程提供有价值的信息。

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.