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

存储器设备是最重要的电子部件之一，并且是现代移动的系统在信息存储和节能计算和通信方面的主要驱动器。下一代存储器器件的一般要求是尺寸减小，这可以增加存储器密度和容量，这对于提供合理低的开关电压的几乎所有应用都是有益的特征。在最近的研究中，我们发现了夹在金属电极之间的原子级薄材料中的记忆效应，这是在标准垂直器件结构中的意外发现。这代表了最薄的存储器设备，可以在各种应用中实现进步，包括脑启发计算，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都很重要。对于存储器设备来说，更重要的是为了针对诸如能耗和信息保留的许多性能参数来设计原子级精简设备。这项研究工作主要集中在基本机制的这个基本问题上，成功完成可以推进存储技术领域，以及示范应用，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这种新的记忆现象背后的物理学原理。此外，若能成功达成研究目标，将可为移动的技术的商业化发展铺平道路，造福社会。过渡金属二硫属化合物（TMD）等原子级薄材料因其在电子学和光电子学方面的多样性前景而引起人们极大的兴趣。已经在各种溶液处理的多层TMD中观察到非易失性电阻切换，包括功能化材料和复合材料，以及基于TMD的混合物，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。最近，我们发现了非挥发性电阻开关行为在单层化学气相沉积的TMD在一个标准的垂直的金属-绝缘体-金属器件结构，在室温下的环境条件下，具有稳定的工作，低过渡电压，高开/关比，低导通电阻和良好的可靠性。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，用于非易失性存储器，神经形态计算和射频开关中的设备应用。然而，造成这一现象的基本机制并不十分清楚。因此，该提案的一部分重点是使用先进的工具研究各种实验，以阐明潜在的物理学。将采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，和温度依赖的运输研究。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，该器件将超过相变非易失性开关的当代指标。该研究目标的成功实现将通过揭示缺陷、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NSF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.