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標題: | 直流高溫超導量子干涉元件磁量計之特性研究:以磁控濺鍍系統製備YBCO薄膜在回收雙晶基板上的製程 Characterization of High-Tc dc-SQUID Magnetometers: Fabrication with Sputtered YBCO Films Deposited on Recycled SrTiO3 Bi-crystal Substrates |
作者: | Tien-Wei Yang 楊天瑋 |
指導教授: | 王立民(Li-Min Wang) |
關鍵字: | 化學機械拋光,SrTiO3雙晶基板,RF濺射系統,高溫超導量子元件,調變電壓,磁通雜訊, high-Tc dc-SQUID,SrTiO3 bi-crystal substrate,chemical mechanical polishing,RF sputtering system,modulation voltage,flux noise, |
出版年 : | 2020 |
學位: | 博士 |
摘要: | 在本論文中,探討以磁控濺鍍系統製備YBa2Cu3O7 (YBCO)薄膜在回收雙晶基板上的製程且利用此製程方式成功製作出高品質的高溫超導量子干涉元件磁量計。在實驗過程中,使用化學機械拋光(Chemical Mechanical Polishing)方法,致使SrTiO3 (STO)雙晶基板的表面粗糙度可以達到0.1-0.2 nm。然後,通過radio freguency (RF)濺射系統將YBCO薄膜沉積在STO雙晶基板 (22.6° 和30°的錯位角)上,臨界溫度Tc和臨界電流密度Jc分別為88 K和0.7 MA / cm2。在蝕刻過程中,使用Ar離子轟擊蝕刻出SQUID電路圖案。 觀察到在STO上c軸取向的YBCO薄膜取決於生長溫度。然後,隨YBCO薄膜上沿著c軸的方向比例的增加,YBCO的傳輸特性增加。但是較高的薄膜生長溫度會使局部YBCO晶界處形成山丘狀的弱連接。在這種情況下,可以從電阻-溫度曲線上觀察到接近Tc(offset)的足部彎曲狀電阻。因此,對於良好的約瑟芬結(Josephson Junction)來說,YBCO晶界生長溫度是非常重要的一件事。 YBCO薄膜的電傳輸性能,其雙晶不同於單晶。 採用最佳化參數下進行薄膜生長和元件製造,元件的調變電壓VPP> 20 μV,磁通量雜訊頻譜在溫度77 K下100 Hz時的磁通雜訊低於15 µΦ0/Hz1/2,其此高溫超導量子元件的良率可高於90%。 In this thesis, we study on the characterization of high-Tc dc-SQUID magnetometers, fabricated with sputtered YBa2Cu3Oy (YBCO) films deposited on recycled SrTiO3 (STO) bi-crystal substrates. On experimental processes, using the chemical mechanical polishing (CMP) method, the surface roughness of recycled STO bi-crystal substrates can be down to 0.3-0.4 nm. Then, the YBCO thin films were deposited on 22.6°- and 30°-misorientation STO bi-crystal substrates by radio frequency (RF) sputtering system, which showed a critical temperature Tc of 88 K and a critical current density Jc of 0.7 MA/cm2. In the etching process, the pattern of SQUID was fabricated using the Ar ion-milling. It was observed that the c-axis orientation of YBCO thin films on STO depends on the growth temperature of YBCO film. Then, the electrical transport properties of YBCO were improved as the part of c-axis oriented YBCO film increases. However, it was found that the higher growth temperature will cause the hill-like structure on R-T curve at the YBCO grain boundary. In this case, a foot-like curvature in the resistance-temperature curve near the Tc (offset) can be observed. In addition, the optimum growth temperature of YBCO bi-crystal grain boundary for a good Josephson Junction is important. The electrical transport properties of YBCO thin films with the bi-crystal grain boundary is different from those of YBCO films without bi-crystal grain boundary. With optimized parameters for thin-film growth and device fabrication, the throughput yield of high-Tc SQUID is higher than 90% for devices with a modulation voltage VPP > 20 μV and a flux noise spectrum below 15 µΦ0/Hz1/2 @100 Hz at 77 K. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/15349 |
DOI: | 10.6342/NTU202001192 |
全文授權: | 未授權 |
顯示於系所單位: | 物理學系 |
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