YBCO／CeO_2／Si多层膜超导材料的分析电镜研究

AEM Study of YBCO/CeO_2/Si Superconducting Multilayer

在具有ＣｅＯ２隔离层的Ｓｉ基片上获得了较高质量的ＹＢａ２Ｃｕ３Ｏ７－ｘ（ＹＢＣＯ）高温超导薄膜。在零磁场下，７７Ｋ时其临界电流密度达到１×１０６Ａ／ｃｍ２。研究发现，ＹＢＣＯ的（００１）面平行于Ｓｉ基片的（１００）面，而ＣｅＯ２过渡层由许多约４０ｎｍ×１００ｎｍ的细小ＣｅＯ２晶粒组成，其取向呈散乱分布。尽管ＣｅＯ２和Ｓｉ之间的晶格错配很小（约０．４％），ＣｅＯ２却不能在Ｓｉ上外延生长，而ＹＢＣＯ却能在取向凌乱的ＣｅＯ２上形成［００１］择优取向。ＣｅＯ２和Ｓｉ的界面处有一层极薄的过度层。ＹＢＣＯ和ＣｅＯ２界面存在Ｙ２ＢａＣｕＯ５（２１１相）。在ＹＢＣＯ薄膜中观察到有与１２３相混生的２４８相。

YBa2Cu3O7-x (YBCO ) thin film has been deposited on Si substrate with CeO2 buffer layer. It shows a high critical transport current density Jc exceeding 1. 0 × 106 A/cm2 at 77 K in zero magnetic field. The orientation relationship of the multilayer film has been studied: The(001) plane of YBCO film is parallel to the(100) plane of St substrate and the CeO2buffer layer consists of many small(40 nm × 100 nm) column-like crystal grains with different orientations. Although the lattice mismatch between CeO2 and Si is very small (about 4% ),CeO2 can not grow epitaxilly on St substrate, while YBCO can grow with c orient preference on scattered oriented CeO2 because of habit growth. A very thin layer exists between Si and CeO2.Several Y2BaCuO5(211 phase) grains exist in the interface of CeO2 and YBCO.