高溫超導釔鋇銅氧薄膜之二氧化鈰緩衝層效應研究

Abstract

本實驗研究利用磁控濺鍍在氧化鎂基板上成長高溫超導釔鋇銅氧薄膜，並以氧化鈰作為緩衝層，預期能有效提升氧化鎂與釔鋇銅氧之間晶格匹配並提升薄膜品質，當樣品成長完成後進行量測，發現以10 nm氧化鈰緩衝層成長的釔鋇銅氧薄膜不論是在相變溫度、釘扎能、臨界磁場、臨界電流密度都有顯著的提升，其中相變溫度由84 K提升至88 K提升了4 K，在磁場微0.5 T下釘扎能從25000 K提升至30000 K，臨界磁場H_(c2,ab)由176 T提升至339 T。 同時在原子力顯微鏡與SEM的影像中可以發現薄膜的表面形貌有非常明顯的改善，在原子力顯微鏡的圖片下可知其面粗糙度最低可達0.6 nm，而未加入緩衝層的樣品其表面粗糙度為4 nm，而臨界電流密度則0.125 A/cm2提升至0.5 A/cm2，同時以Dew-Hughes理論分析推論其，釘扎中心的幾何結構則是從二維變成三維。

In this experiment, a high-temperature superconducting YBCO film was grown on a MgO substrate by magnetron sputtering, and CeO2 was used as a buffer layer. When the sample was grown and measured, it was found that the YBCO film grown with the 10 nm CeO2 buffer layer has a significant improvement in phase transition temperature, pinning energy, critical magnetic field, and critical current density. The Tc increases from 84 K to 88 K, the pinning energy increases from 25000 K to 30,000 K and the critical magnetic field Hc2,ab increases from 176 T to 339 T. At the same time, the surface morphology of the thin film can obviously improve in the images of AFM and SEM. Under the picture of AFM, the surface of the sample that has buffer layer has its minimum roughness at 0.6 nm and the sample without the buffer layer has a surface roughness at 4 nm, the critical current density is increased from 0.125 A/cm2 to 0.5 A/cm2. At the same time, Dew-Hughes theoretical analysis is used to infer that the geometry of the pinning center is changed from two-dimensional to three-dimensional.