Mechanistic and Device Studies of the New Observation of Non-Volatile Resistance Switching in Atomic Sheets

存储设备是最重要的电子元件之一，也是现代移动系统在信息存储、节能计算和通信方面的主要驱动力。对下一代存储设备的一般要求是减小尺寸，这可以增加存储密度和容量，这对几乎所有应用都是有益的，只要开关电压相当低。在最近的研究中，我们在夹在金属电极之间的原子薄材料中发现了记忆效应，这是在标准垂直器件结构中意想不到的发现。这代表了最薄的存储设备，可以实现各种应用的进步，包括大脑启发计算，信息存储和射频开关。对于任何用例场景，理解现象背后的基本机制是很重要的。对于存储设备来说，更重要的是为了设计一些性能参数（如能耗和信息保留）的原子级薄设备。这项研究工作主要集中在基本机制的基本问题上，成功完成可以推进存储技术领域和范例应用，特别是射频开关。这项工作将采用各种先进的实验工具来阐明导致这种新记忆现象的潜在物理原理。此外，研究目标的成功实现将为移动技术的商业发展铺平道路，造福社会。过渡金属二硫族化合物（TMDs）等原子薄材料因其在电子学和光电子学领域的广阔前景而引起了人们的广泛关注。非易失性电阻开关已经在各种溶液处理的多层tmd中被观察到，包括功能化材料和复合材料，以及基于tmd的混合材料，其中电阻可以在高电阻状态和低电阻状态之间调制，并且随后在没有任何电源的情况下保持不变。最近，我们在标准的垂直金属-绝缘子-金属器件结构中发现了单层化学气相沉积tmd的非挥发性电阻开关行为，该结构具有低转换电压、高开关比、低导通电阻和良好的可靠性，在室温环境条件下稳定运行。这一发现激发了对二维半导体和绝缘体中电子和离子输运的新研究，这些器件应用于非易失性存储器、神经形态计算和射频开关。然而，造成这种现象的基本机制尚不清楚。因此，本提案的一部分重点是研究使用先进工具的各种实验，以阐明潜在的物理。使用的工具包括扫描隧道显微镜和光谱学、透射电子显微镜、导电原子力显微镜和温度依赖输运研究。研究工作的另一部分是设计用于高性能射频开关应用的原子级薄存储器件，该器件将超过当代相变非易失性开关的指标。研究目标的成功完成将通过揭示缺陷、原子和离子的动力学和能量学，以及产生可靠记忆效应所需的条件，大大促进tmd的科学和应用。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Memory devices are among the most important electronic components and the main driver for modern mobile systems in terms of information storage and energy-efficient computation and communication. A general requirement for future generation memory devices is size reduction, which can increase the memory density and capacity, a beneficial feature for virtually all applications provided the switching voltage is reasonably low. In recent research, we discovered memory effect in atomically-thin materials sandwiched between metal electrodes, an unexpected discovery in a standard vertical device structure. This represents the thinnest memory devices and can enable advancements in various applications including brain-inspired computing, information storage, and radio-frequency switches. For any use case scenarios, it is important to understand the basic mechanism behind a phenomenon. All the more important for memory devices in order to engineer the atomically-thin devices for a number of performance parameters such as the energy consumption and information retention. This research effort focuses primarily on this basic question of fundamental mechanism(s), which successfully accomplished can advance the field of memory technology, and exemplar applications, specifically radio-frequency switches. The effort will employ a variety of advanced experimental tools to elucidate the underlying physics responsible for this new memory phenomenon. Furthermore, successful achievement of the research objective will pave the path towards commercial development to benefit society in mobile technology.Atomically-thin materials such as transition metal dichalcogenides (TMDs) have drawn great interest due to its diverse prospects in electronics and optoelectronics. Non-volatile resistance switching has been observed in various solution-processed multi-layer TMDs, including functionalized materials and composites, and TMD-based hybrids, where the resistance can be modulated between a high-resistance state and a low-resistance state, and subsequently retained absent any power supply. Recently, we discovered non-volatile resistance switching behavior in monolayer chemical vapor deposited TMDs in a standard vertical metal-insulator-metal device structure with stable operation under ambient condition at room temperature with low transition voltage, high on/off ratio, low ON resistance and good reliability. This discovery inspires new research on electron and ion transport in two-dimensional semiconductors and insulators for device applications in non-volatile memory, neuromorphic computing, and radio-frequency switches. However, the basic mechanism responsible for the phenomenon is not well understood. As such, this proposal effort focuses in one part to research a variety of experiments using advanced tools to elucidate the underlying physics. The tools to be employed include scanning tunneling microscopy and spectroscopy, transmission electron microscopy, conductive-atomic force microscopy, and temperature dependent transport studies. The other part of the research effort is to design the atomically-thin memory device for high-performance radio-frequency switch applications that will exceed the contemporary metrics for phase-change non-volatile switches. The successfully accomplishment of the research objectives will significantly further the science and applications of TMDs by shedding light on the dynamics and energetics of defects, atoms and ions, and the required conditions that result in reliable memory effect.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.