电场调控钙钛矿锰氧化物金属-绝缘体转变及机制研究

Gate control of metal-insulator transition in correlated electron oxides has been an emerging topic in modern condensed matter physics and material research recently. Perovskite manganite, a typical class of correlated electron oxides, is one of the best candidates for field-effect modulation research, due to its rich phase diagram induced by strong coupling between charge, spin, orbital, and lattice degrees of freedom. In this project, we will grow a series of strontium-doped lanthanum manganite films by laser molecular beam epitaxy, and prepare electric double layer transistors by micro-fabrication techniques. Then, we will realize the electric-field control of metal-insulator transition in manganite films, and investigate the effect of oxygen content, doping density, film thickness, and strain in the films on the electric-field modulation of resistivity. Currently, there has been controversy on the underlying mechanism for the electric-field modulation of resistivity in electric double layer transistors. To understand whether the oxygen vacancies play an important role in the field-effect modulation, we will utilize aberration-corrected scanning transmission electron microscopy with atomic resolution and sensitivity for light elements to measure the content of oxygen vacancies under various gate voltages, and study the differences of the electric-field modulation between samples fabricated under various oxygen pressures. Then the physical origins behind the novel phenomena induced by the field-effect will be revealed. It is hoped that our study will provide the scientific basic for the future development of multifunctional oxide devices.

通过电场效应调控关联电子氧化物的金属-绝缘体转变，近几年来逐渐成为凝聚态物理和材料科学研究前沿的热点之一。钙钛矿锰氧化物是一类典型的关联电子氧化物，由于电荷、自旋、轨道、晶格自由度之间强烈的耦合展现了丰富的特性，是进行场效应调控的理想体系。本项目利用激光分子束外延技术生长一系列锶掺杂的锰酸镧外延薄膜，通过微加工技术制备成双电层晶体管结构，用于材料金属-绝缘体转变的电场调控，研究制备氧压、掺杂浓度、薄膜厚度、衬底应力对体系场效应调控的影响。针对目前场效应调控机制存在的争议，我们将利用球差校正扫描透射电镜技术能够直接观测到氧原子的优势，结合不同氧含量薄膜材料的场效应调控结果，重点研究氧空位在场效应调控中所起的作用，进而揭示电场效应诱导新颖物性的物理根源，为发展新一代多功能氧化物电子器件提供科学基础。

通过电场效应调控关联电子氧化物的金属-绝缘体转变，近几年来逐渐成为凝聚态物理和材料科学研究前沿的热点之一。钙钛矿锰氧化物是一类典型的关联电子氧化物，由于电荷、自旋、轨道、晶格自由度之间强烈的耦合展现了丰富的特性，是进行场效应调控的理想体系。我们利用激光分子束外延技术生长一系列锶掺杂的锰酸镧外延薄膜，研究了氧空位影响锰酸镧薄膜的物理机制。通过微加工技术制备成双电层晶体管结构，实现了高达四个量级以上的金属-绝缘体转变，并利用球差校正扫描透射电镜技术能够直接观测到氧原子的优势，结合不同氧含量薄膜材料的场效应调控结果，揭示电化学反应产生的氧空位在场效应调控中所起的重要作用。在项目执行期间，共发表SCI论文19篇，其中第一/通讯作者文章8篇，申请发明专利5项，在国内外学术会议获得5次邀请报告，超额完成了本项目的既定目标。