研究生: |
賴一鳴 Yi-Ming Lai |
---|---|
論文名稱: |
以離軸濺鍍的方式來研究45度同質雙磊晶高溫超導約瑟芬結 Study of the Homo-Biepitaxial YBCO grain boundary junction by using the off-axis RF sputtering |
指導教授: |
齊正中
Cheng-Chung Chi |
口試委員: | |
學位類別: |
碩士 Master |
系所名稱: |
理學院 - 物理學系 Department of Physics |
論文出版年: | 2006 |
畢業學年度: | 94 |
語文別: | 英文 |
論文頁數: | 54 |
中文關鍵詞: | 釔鋇銅氧 、濺鍍 、約瑟芬結 、高溫超導 |
外文關鍵詞: | YBCO, sputtering, grain boundary junction |
相關次數: | 點閱:3 下載:0 |
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我們使用離濺鍍法在YSZ[100]基板上成長YBCO高溫超導薄膜,並成功的在不同鍍膜溫度下得到相對於YSZ[100]軸兩種不同轉向的YBCO薄膜,分別為在825℃成長的YBCO[100]//YSZ[100] (0度) 薄膜及在670℃成長的YBCO[110]//YSZ[100] (45度) 薄膜,我們所得到的YBCO薄膜其臨界溫度約在86K~88K,而其臨界電流密度在5K時為9×10^6~1.14×10^7 A/cm2。
運用此兩種不同轉向的YBCO薄膜,我們可以來製做高溫超導約瑟芬結,首先,先在825℃成長一層約50 nm厚的YBCO緩衝層,隨即用離子蝕刻把一半的YBCO緩衝層蝕刻掉,接下來在670℃成長約150 nm厚的YBCO薄膜;成長在緩衝層上頭的YBCO薄膜可維持與緩衝層一樣的轉向 (0度),而成長在被離子蝕刻過的基板上的YBCO薄膜則為 45度轉向。我們最後得到的45度約瑟芬結其臨界電流密度在4.2K時為10^3~10^4 A/cm^2,而其臨界電流與外加磁場的關係為非正常的Fraunhofer-pattern。
By using the off-axis RF magnetron sputtering method, we have fabricated YBCO thin films on YSZ [100] substrates with two distinct in-plane orientations, namely, YBCO [100] // YSZ [100] (0^0 in-plane orientation) at 825^0C and YBCO [110] // YSZ [100] (45^0 in-plane orientation) at 670^0C. Both thin films have critical temperatures T_{C0} in the range of 86~88K and critical current densities at 5K in the range of 9 X 10^6 A/cm^2 ~ 1.2 X 10^7 A/cm^2. To fabricate the 45^0 grain boundary junctions, we first deposit a thin YBCO [100] film at 825^0C on the substrate and remove part of the film by ion-milling. Then a thicker YBCO film is deposited at 670^0C. We show that the film
deposited on the ion-bombarded substrate can maintain its 45^0 in-plane orientation while the film deposited on the YBCO [100] film keeps the 0^0 in-plane orientation. The critical currents densities of our 45^0 grain boundary are in the range of 10^3~10^4 A/cm^2 at 5K and the modulation curves are anomalous Fraunhofer patterns because of the inhomogeneous critical current densities result from the faceting effect and the d_{x^2-y^2} symmetry of the order parameter.
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