鉈鋇鈣銅氧1223相高溫超導薄膜之製備與特性研究

Abstract

本研究已成功發展出以直流濺鍍法配合適當的熱處理製程製備單相,c-軸 成長之鉈系1223相高溫超導薄膜之製成技術。此外,除了找出成長高品質 鉈系1223相之條件外更根據我們對薄膜成長機制的瞭解成功地設計了兩套 不同多階段熱處理製程,以進一步改善薄膜之晶粒結構、表面狀態及超導 特性等。結果顯示,薄膜之超導溫度可達110K,尤有甚者,以本實驗所揭露 之製程方法所獲得之薄膜展現此一系統至目前為止之最高傳輸臨界電流密 度,顯示以此一簡單之自製系統製備高品質薄膜之可行性。此一結果不僅 更進一步証實了我們對鉈系1223相薄膜之成長機制的正確觀念,更明白指 出改善以符和實際應用所需之可行方向。 Singe phase, c-axis oriented TlBa2Ca2Cu3O9±δ superconducting thin films with zero-resistance transition temperature(Tco) above 110K have been obtained by DC- sputtering followed by proper post-annealing process. In particular, the films obtained by the present process has displayed the best transport critical current results reported to-date for this material, indicating the viability of the simple deposition technique in obtaining high quality films. From the fundamental point of view, however, it have been found that, with the exact stoichiometry composition to start, the post annealing conditions for forming pure Tl-1223 phase are extremely restrictive. It is also noted that, in addition to the harshness of the treatment conditions, the mechanism of the formation of Tl-1223 phase may be dominated by the nucleation and growth kinetics of the particular phase. There is no sequential phase transformation between different phase when the thermodynamical conditions provided in practice were fixed. As a result, the morphology and properties of the films can be improved by prolonged treatment with some proper arrangement. Details of the experimental results will be presented and discussed.