- 學位論文
應用超導量子干涉元件掃描儀系統研究量子磁通渦漩滲入第二類超導體薄膜之行為(Construction of a Scanning SQUID Microscope and study of individual vortex penetration in type II superconducting thin film)
Construction of a Scanning SQUID Microscope and study of individual vortex penetration in type II superconducting thin film
摘要
超導量子干涉元件掃描儀已經被廣泛的應用於量子磁通束的分佈、超導電子對的相位對稱性確認、及超導材料的雜質分佈等等。在架構超導量子干涉元件掃描儀的種種課題裡，最為重要的一環便是設計及製造一個在實際量測操作時擁有高訊雜比的超導量子干涉元件。很幸運的，藉由與中央研究院天文所王明杰博士所領導的超導元件實驗室的合作，利用他們已發展成熟穩定的半導體製程技術，我們可以利用三層夾心結構(Nb-AlOx-Nb)來製作高品質的約瑟芬結，進而製作出良好的超導量子干涉元件並應用於超導量子干涉元件掃描儀上。在這篇論文裡，我將簡單說明我們的超導量子干涉元件特性、製作過程，以及超導量子干涉元件掃描儀的架設過程。 我們也利用金屬濺鍍的設備製作不同幾何形狀的鈮薄膜，接著在應用架設完成的超導量子干涉元件掃描儀來觀察相對於不同幾何形狀的超導薄膜上的磁場分佈。我們也了解到在不同幾何形狀上，超導電流不連續性可以用來解釋這些磁場的分佈情形。超導量子干涉元件掃描儀也幫助我們觀察量子磁通束的滲入行為、邊緣量子磁通捕獲現象以及正、反量子磁通的分佈情形。在這篇論文裡，我將介紹兩個主要描述磁通量子束滲入第二類超導體行為的理論，一是比恩-李文斯頓模型，一是Zeldov等人的理論計算。從我們的實驗結果，我們也發現到對一個非理想的第二類超導薄膜，磁通量子束滲入第二類超導體行為並不能完全的藉由這兩個理論來描述。我們也觀察到一些關於正量子磁通束的捕獲分佈如何影響反量子磁通束的滲入行為的有趣的結果。
並列摘要
The Scannign SQUID Microscope (SSM) system has been widely used in flux distribution image, pairing symmetry verification, defects distribution,...etc. One of the important issues in constructing the SSM system is to design and fabricate a practical dc SQUID which has high SNR during operation. Fortunately, with the collaboration to Superconducting Device Lab which was led by the associate research fellow of Academia Sinica Institute of Astronomy & Astrophysics (ASIAA), Dr. Wang, Ming-Jye, by using our own Nb-AlOx-Nb technology, we have successfully developed a SSM system. In this paper, I will discuss about the characteristics of our home-made dc SQUID and the performance of our SSM system briefly. We have deposited some Nb thin film with different geometry, and imaged the magnetic field distribution by SSM system. The current discontinuity consideration is consistence to our magnetic field distribution images. The SSM system also helps us in observing the vortices penetration behavior, the edge vortices pinning and the distribution of vortex and anti-vortex. In this paper, I will show you some observations about the flux images of the practical Nb thin film. I will introduce two different theories in discussing the vortex penetration of type II superconductor, the Bean-Livingston model and the calculations from Zeldov et al. However, our observations about the vortex penetration behavior of practical type II superconducting thin film were not consistent with these theories fully. We also observed some interesting results about the vortex pinning related to the anti-vortex penetration distribution.