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

非技术描述：这项提议旨在解决离子导电玻璃中电荷和质量输运的一个基本问题：电场如何在金属掺杂玻璃(含S、Se或Te)中产生电子传导路径？在较强的外电场作用下，根据电场的方向，在固体电解液内部形成或湮灭电子传导路径。观察到的外场对电子传导路径的可逆产生/湮灭模拟了二进制系统的0和1状态，并且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器技术。本项目的目标是通过综合实验/理论方法来了解导电丝的破坏和形成机理。该项目的成功提供了对新兴的CBRAM技术的基本了解，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邀请通常在科学和工程领域代表性较低的学生参与研究项目而进一步扩大。暑期实习通过在校本科生研究体验计划向本科生提供。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的自闭症谱系障碍儿童提供服务。技术细节：基于固体电解质玻璃的快离子导体比晶体导体具有许多优势。例如，掺银硫化物玻璃表现出极高的离子导电性。这些材料的一个有趣的转折是，在强大的外部电场下，在固体电解质内部产生了电子传导路径。人们普遍认为，通过场驱动的电化学反应形成金属丝是提高电子传导性的原因。然而，这种观点导致了一种错误的预测，即在外场作用下，金属离子和固体电解质主体同时发生超快运动。这项研究的一个假设是，由外加电场产生的电子导电丝不是由简单的金属制成，而是复杂的半导体化合物，涉及被离子陷阱中心捕获在固体电解质中的浓缩离子。选取了典型的金属掺杂硫系玻璃(即银和铜掺杂的Ge-Se和Sb-Te)进行了研究。应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。采用了一种新的模拟技术，称为实验约束分子弛豫(ECMR)，以确保理论与实验的最大一致性。采用实验/理论相结合的方法，研究了电场作用下电子导电丝的结构、性质和动力学特性。这个项目提供了对电子导电丝形成动力学和结构-性能关系的原子洞察力。参与该项目的本科生和研究生接受尖端研究设施方面的培训，例如阿贡国家实验室和俄亥俄州超级计算中心的先进光子源和纳米材料中心。向患有自闭症谱系的儿童提供外展服务，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.