Growth of High-Temperature Oxide Superconductor Thin Films on Ultrasmooth Substrates and Elucidation of Their Growth Mechanism.

这是非常重要的，要知道氧化物超级导体的增长机制，以获得具有原子表面平坦性的高质量电影。在这项研究中，我们在MgO（100）上沉积了YBCO薄膜，由原子力显微镜（AFM）探测和调查了早期生长阶段的YBCO薄膜。并讨论了表面结构对YBCO薄膜增长机制和表面结构的影响，MgO的原子平坦表面（100）具有不同地形宽度和高度的步骤基底已被H-D22 H-D20蚀刻和高温退火所发现，c-axis oriented YBCO thin films were grown on such substrates by sputtering and Observed the early stages of the films growth by AFM。三维岛屿结构沿着3个单元单元格的台阶边缘观察（U.C.）厚的YBCO电影在宽阳台上长大，高台阶高度。这被认为是因为YBCO的沉积物种最好在步骤边缘和形式岛结构中捕获，所以当地形宽度大于沉积物种的扩散长度和步骤高度大于YBCO单元长度的宽度。在另一边， 2D谷物和没有岛屿观察到电影生长在薄膜上，有狭窄的地形宽度和低台阶高度，当电影厚度为3u.c。Growth mode on such substrates changed from 2 D layer-by-layer growth to 3 D ledge growth at the film thickness around 7 u.c.当电影厚度为lOu.c.时，螺旋结构的启动被观察到。它包括YBCO电影的增长机制，当电影的厚度比lOu.c.厚时，YBCO电影的增长机制也通过化学蚀刻使用硫基和磷酸盐以及ZnO和GaN薄电影在它们上生长时。“薄电影在阶梯上生长的晶体质量比在非治疗性物质上生长的要好。”

It is very important to know the growth mechanism of oxide superconductors to obtain high-quality films with atomic surface flatness. In this study, we deposited YBCO thin films on MgO(100) ultra smooth step substrates by sputtering and investigated the early stages of the growth by atomic force microscopy (AFM). And discussed the influence of the surface structure of the substrates on the growth mechanism and surface structure of YBCO films.Atomically flat surface of MgO(100) step substrates with different terrace width and step height have been obtained by HィイD22ィエD20 etching and high-temperature annealing, c-axis oriented YBCO thin films were grown on such substrates by sputtering and observed the early stages of the films growth by AFM. 3D island structures were observed along the step edges for 3 unit cell(u.c.) thick YBCO films when grown on wide terrace width and high step height. It is considered that the deposited species of YBCO are preferentially captured at the step edges and form island structures there when the terrace width is wider than diffusion length of deposition species and the step height is much higher than the unit cell length of YBCO. On the other hand, 2D grains and no island were observed on the films grown on the substrates with narrow terrace width and low step height when the film thickness was 3u.c. Growth mode on such substrates changed from 2D layer-by-layer growth to 3D ledge growth at the film thickness around 7u.c. The initiation of spiral structures was observed when the film thickness is lOu.c. It is concluded that the growth mechanisms of YBCO film changed from 3D ledge growth to spiral growth when the film thickness is thicker than lOu.c.Ultra smooth sapphire step substrates were also obtained by chemical etching using sulfuric and phosphoric acids and ZnO and GaN thin films were grown on them by sputtering. The crystal quality of thin films grown on step substrate was better than that on non-treated substrates.