Science of Electron-conducting Filaments in Ion-conducting Chalcogenide Glasses

非技术描述：本提案旨在解决离子导电玻璃中电荷和质量传输的基本问题：电场如何在金属掺杂玻璃（含有S， Se或Te）中创建电子导电路径？在强外电场下，固体电解质内部的电子传导路径根据电场方向的不同而产生或湮灭。观察到的电子传导路径的可逆创建/湮灭通过外场模拟二进制系统的0和1状态，是导电桥接随机存取存储器（CBRAM）的基础，CBRAM是一种基于双极电阻开关的新型非易失性存储技术。本项目旨在通过实验/理论相结合的方法来了解导电细丝的破坏和形成机制。该项目的成功提供了对新兴CBRAM技术的基本理解，并有望将电子绝缘玻璃转变为电子导电玻璃。这项研究的影响通过吸引通常在科学和工程领域代表性不足的学生参与研究项目而进一步扩大。暑期实习是通过本科生校内研究经验项目提供给本科生的。通过科学演示、研讨会和夏令营活动，向俄亥俄州阿巴拉契亚地区患有自闭症谱系障碍的儿童提供服务。技术细节：基于固体电解质玻璃的快离子导体比晶体导体有许多优点。例如，掺银硫系玻璃表现出极高的离子电导率。这些材料的一个有趣的变化是，在强大的外部电场下，固体电解质内部会产生电子传导路径。人们普遍推测，通过场驱动电化学反应形成金属细丝是电子导电性增强的原因。然而，这种观点导致了一个错误的预测，即金属离子和固体电解质主体在外场下同时发生超高速运动。该基金的一个假设是，由外电场产生的导电细丝不是由简单的金属构成的，而是由复杂的半导体化合物构成的，这些化合物包括被固体电解质中的离子阱中心捕获的浓缩离子。选择了典型的金属掺杂硫系玻璃（即Ag和Cu掺杂Ge-Se和Sb-Te）进行研究。采用先进的实验和理论技术来了解外场作用下固体电解质中的电荷和质量输运。采用一种新的模拟技术——实验约束分子弛豫（ECMR）来保证理论与实验的最大一致性。采用实验/理论相结合的方法研究了电场作用下导电细丝的结构、性能和动力学。本项目提供了对导电细丝形成动力学和结构-性能关系的原子洞察。参与该项目的本科生和研究生接受尖端研究设施的培训，如阿贡国家实验室的先进光子源和纳米材料中心以及俄亥俄超级计算中心。向自闭症谱系儿童提供外展服务，以提高他们对大学教育和信息技术职业的兴趣。

NON-TECHNICAL DESCRIPTION: This proposal aims to address a fundamental question of charge and mass transport in ion-conducting glasses: how does an electric field create an electron-conducting path in metal-doped glasses (that contain S, Se or Te)? Under a strong external electric field, an electron-conducting path is created or annihilated inside the solid electrolyte depending on the direction of the electric field. The observed reversible creation/annihilation of electron-conducting paths by external fields mimics 0 and 1 states of a binary system and is the basis underlying conductive bridging random access memory (CBRAM), a novel non-volatile memory technology based upon bipolar resistive switching. The goal of this project is to understand the destruction and formation mechanism of the conductive filaments through integrated experiment/theory approaches. Success of this project provides fundamental understanding of the emerging CBRAM technology and promises transformation of electronically insulating glasses to electronically conducting glasses. The impact of this research is broadened further by engaging students typically underrepresented in science and engineering to participate in the research project. Summer internships are offered to undergraduate students through the on-campus Research Experience for Undergraduates program. Outreach to children with autism spectra disorder in Appalachian Ohio is offered through science demonstrations, workshops and summer camp activities.TECHNICAL DETAILS: Fast-ion conductors based upon solid electrolyte glasses have many advantages over their crystalline counterparts. For example, Ag doped chalcogenide glasses exhibit extremely high ionic conductivity. An interesting twist for these materials is that under a strong external electric field, an electron-conducting path is created inside the solid electrolyte. It is widely speculated that formation of metal filaments through field-driven electrochemical reactions is responsible for the enhanced electronic conductivity. However, this view leads to an erroneous prediction that superfast motion of both the metal ions and the solid electrolyte host occurs simultaneously under the external field. A hypothesis of this grant is that the electron-conducting filaments created by the external electric field are not made simply of metal, but complex semiconducting compounds that involve concentrated ions trapped by the ion-trap centers in the solid electrolytes. Prototypical metal-doped chalcogenide glasses (i.e., Ag and Cu doped Ge-Se and Sb-Te) were selected for study. Advanced experimental and theoretical techniques are applied to understand the charge and mass transport in the solid electrolytes under external fields. A novel simulation technique called experimentally constrained molecular relaxation (ECMR) is used to ensure maximal coincidence between theory and experiment. Structure, properties and dynamics of the electron-conducting filaments generated by the electric field are studied through the integrated experiment/theory approach. This project provides atomistic insight into the dynamics of filament formation and structure-property relations of the electron-conducting filaments. Undergraduate and graduate students participating in this project are trained on cutting-edge research facilities such as those in Advanced Photon Source and Center for Nanoscale Materials at Argonne National Lab and the Ohio Supercomputing Center. Outreach to children with autism spectral order is offered to enhance their interest in college education and careers in information technology.