Cation Ordering by Atomic Layer Engineering of Strongly Correlated Oxides

该方案解决了具有通式ABO3的强相关钙钛矿氧化物薄膜中A位和b位的化学取代紊乱。由于强电子相关性和电子-声子耦合，这些材料显示耦合相变，潜在的科学有趣现象和技术上有前途的功能。由于化学取代（掺杂）而产生的阳离子或淬火无序，强烈影响相变，抑制其临界温度并掩盖相关氧化物的固有基本行为。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（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，其中层状和/或棋盘型阳离子有序将实现。通过晶格匹配和晶格不匹配的衬底，可以得到相干应变和无应变的有序钙钛矿。整体和局部晶体结构和化学成分将通过x射线衍射/反射仪以及扫描隧道和透射电子显微镜到原子尺度进行分析。局部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。揭示了阳离子有序对人工有序钙钛矿晶格中电子和磁性能的改善以及Tc的增加的影响。

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.