Cation Ordering by Atomic Layer Engineering of Strongly Correlated Oxides

该提案解决了具有通式ABO3的强关联钙钛矿氧化物薄膜中A位和B位的化学取代无序问题。由于强烈的电子关联和电子-声子耦合，这些材料显示出耦合的相变，潜在的科学有趣的现象和技术上有希望的功能。化学取代(掺杂)产生的阳离子或猝灭的无序对相变有很大的影响，抑制了相变的临界温度，掩盖了相关氧化物的本征基本行为。我们提出了一种基于原位控制原子层外延和应变工程的相关氧化物阳离子有序薄膜的生长方法，这两种方法都是在金属有机气溶胶沉积(MAD)技术中实现的。三维(3D)和二维(2D，Ruddlesden-Popper)钙钛矿的A位有序修饰以及B位有序双钙钛矿将以人工超晶格的形式外延生长，其中将实现层状和/或棋盘式的阳离子有序化。通过使用晶格匹配和晶格失配的衬底，将获得相干应变和无应变的有序钙钛矿。全球和局部的晶体结构和化学成分将通过X射线衍射/反射术以及扫描隧道和透射电子显微镜进行分析，直至原子尺度。局域晶格应变和电子电荷的分布将在纳米尺度和原子尺度上被量化。阳离子有序化对人工有序钙钛矿晶格中电子和磁性的改善以及T_c的增加的影响将被揭示。

The proposal addresses chemical substitutional disorder on A- and B-sites in thin films of strongly correlated perovskite oxides with general formula ABO3. Because of strong electronic correlations and electron-phonon coupling these materials display coupled phase transitions, underlying scientifically interesting phenomena and technologically promising functionalities. Cation or quenched disorder, arising as a result of chemical substitution (doping), strongly affects phase transitions, suppressing their critical temperature and masking the intrinsic fundamental behavior of correlated oxides.We propose a growth approach for the cation-ordered films of correlated oxides based on in-situ controlled atomic layer epitaxy and strain engineering, both realized within a metalorganic aerosol deposition (MAD) technique. The A-site ordered modifications of three- (3D) and two-dimensional (2D, Ruddlesden-Popper) perovskites as well as B-site ordered double perovskites will be epitaxially grown in the form of artificial superlattices, in which a layered and/or checker-board types of cation ordering will be realized. By using lattice-matched and lattice-mismatched substrates, coherently strained and strain-free ordered perovskites will be obtained. Global and local crystalline structure and chemical composition will be analyzed by X-ray diffraction/reflectometry as well as by scanning tunneling and transmission electron microscopy down to the atomic scale. Distributions of local lattice strain and electronic charge will be quantified at the nanoscale and atomic scale. The impact of cation ordering on the improvement of electronic and magnetic properties and on the increase of Tc in artificially ordered perovskite lattices will be disclosed.