Controlling Defects in Transition Metal Oxide Thin Films

非技术描述：活性成分材料的稳定性和耐久性通常决定着电子设备的性能和可靠性。此外，器件性能经常受到原子级结构缺陷或不同材料之间界面的存在的影响。虽然这些缺陷和界面在许多情况下是不可避免的，但我们对如何控制和操纵它们对材料性能的影响的理解仍然不清楚。因此，原子尺度的缺陷或界面对材料宏观行为影响的基础研究对于继续开发下一代高速计算机内存存储和能量转换设备至关重要。含有过渡金属（如钴或钛）和氧的陶瓷材料由于其可用于创新记忆存储应用（例如硬盘驱动器）和可靠的废热回收的特性而引起了越来越多的科学关注。在这个研究项目中，PI结合了原子分辨率扫描透射电子显微镜和计算材料建模，以建立对两种可用于此类设备的特定陶瓷氧化物材料缺陷的控制。本研究的一个独特之处在于，缺陷和界面对这些陶瓷氧化物材料功能特性的影响是在显微镜柱内以原子分辨率使用新颖的原位实验进行测试的。这种方法允许PI建立对缺陷对新器件的整体性能和可靠性的影响的控制。研究活动涉及科学和工程本科生和研究生的教育和培训，包括代表性不足的少数民族。特别是，通过伊利诺伊大学芝加哥分校的PI本科生研究期刊，促进了本科生参与积极的研究项目。技术细节：本研究项目的目的是利用原子分辨率扫描透射电子显微镜，第一性原理密度泛函理论（DFT）材料建模和分子束外延，以及脉冲激光薄膜沉积的综合研究方法来研究两种陶瓷氧化物薄膜体系。PI已经组建了一个跨学科的专家团队，以发展对过渡金属氧化物薄膜的输运和铁性质的缺陷和掺杂的作用的基本理解。更具体地说，研究了氧空位、掺杂剂和界面对生长在砷化镓上的钙钛矿过渡金属氧化物薄膜铁电性能的影响，以及对非相应层状过渡金属氧化物薄膜热电输运的影响。通过结合最新的原位电场偏置和样品加热实验、原子分辨率成像和光谱以及第一性原理材料建模，研究了复杂过渡金属氧化物陶瓷薄膜中的缺陷化学。该项目的一个重要特点是通过培养最先进的原位扫描透射电子显微镜和理论材料物理学的本科生和研究生，将研究和教育结合起来。

NON-TECHNICAL DESCRIPTION: The stability and durability of an active component material frequently governs the performance and reliability of electronic devices. Moreover, the device performance is often influenced by the presence of atomic-level structural defects or interfaces between dissimilar materials. While these defects and interfaces are in many instances unavoidable, our understanding of how to control and manipulate their effect on a material's properties still remains unclear. Accordingly, fundamental research of the atomic-scale impact of defects or interfaces on a material's macroscopic behavior is essential to continuing the development of next generation high-speed computer memory storage and energy-conversion devices. Ceramic materials that contain transition metals, such as cobalt or titanium, and oxygen have attracted increasing scientific attention due to their properties that can be used in innovative memory storage applications (e.g., hard-drives) and in reliable waste-heat recovery. In this research project, the PI combines atomic-resolution scanning transmission electron microscopy and computational materials modeling to establish control over defects in two specific ceramic oxide materials that can be used in such devices. One unique aspect of this research is that the effects of defects and interfaces on the functional properties of these ceramic oxide materials are tested inside the microscope column at atomic resolution using novel in situ experiments. This approach allows the PI to establish control over the effects that defects have on the overall performance and reliability of a novel device. The research activities involve education and training of science and engineering undergraduate and graduate students, including underrepresented minorities. In particular, the participation of undergraduate students in active research projects is fostered through the PI's Journal of Undergraduate Research at the University of Illinois at Chicago.TECHNICAL DETAILS: The objective of this research project is to use a comprehensive research approach consisting of atomic-resolution scanning transmission electron microscopy, first principles density functional theory (DFT) materials modeling and molecular beam epitaxy, as well as pulsed laser thin film deposition to study two ceramic oxide thin film systems. The PI has assembled an interdisciplinary team of experts to develop a fundamental understanding of the role that defects and dopants play on the transport and ferroic properties of transition metal oxide thin films. More specifically, the effects of oxygen vacancies, dopants and interfaces on the ferroelectric properties of perovskite transition metal oxide thin films grown on GaAs and on the thermoelectric transport in incommensurately layered transition metal oxide thin films are studied. By combining state-of-the-art in situ electric-field biasing and sample heating experiments with atomic-resolution imaging and spectroscopy, and first-principles materials modeling, the defect chemistry in complex transition-metal oxide ceramics thin films is studied. An important feature of this program is the integration of research and education through the training of undergraduate and graduate students in state-of-the-art in situ scanning transmission electron microscopy and theoretical materials physics.