Title

高溫超導釔鋇銅氧不同厚度微橋的約瑟芬效應

Translated Titles

Josephson Effects in High-Tc YBCO Variable-Thickness Bridges

Authors

詹逢駿

Key Words

聚焦離子束 ; 約瑟芬接面 ; 超導量子干涉元件 ; Focused Ion Beam ; VTB ; Josephson junctions ; DC SQUID

PublicationName

中興大學奈米科學研究所學位論文

Volume or Term/Year and Month of Publication

2011年

Academic Degree Category

碩士

Advisor

吳秋賢

Content Language

繁體中文

Chinese Abstract

本論文中,我們將討論利用控制連結區域(link region)的不同厚度來製作高溫超導約瑟芬接面與直流式超導量子干涉元件。利用聚焦離子束(Focused Ion Beam)製作奈米尺度下不同厚度微橋(Variable Thickness Bridge-VTB)的約瑟芬接面,若將接面厚度控制至奈米尺度下,微橋將呈現弱連結效應及產生穿遂效應。 我們利用聚焦離子束在厚度150 nm、寬度1 - 3 μm的釔鋇銅氧(YBa2Cu3O7-X) 微橋上進行局部性的離子蝕刻,將接面厚度控制於40 - 90 nm,若微橋超導性受到破壞,我們將進行一次退火。接面厚度介於70-80 nm時,77 K下量測到的電壓-電流曲線,呈現近似電阻分路結模型(R.S.J. model) ,且臨界電流遵守 Ic ∝ (1-T/Tc)α ,在靠近Tc 時,α=2;隨著溫度降低,α=1與Ic為線性化關係,呈現出超導-金屬-超導的接面特性。照射3.02 - 14.64 GHz的微波時,亦成功量測到定電壓台階曲線 (Shapiro step),且隨著功率增加其台階電流寬度以類似貝索函數(Bessel-function)趨勢受抑制。於70 K下,DC SQUID也成功量測出磁通-電壓響應曲線,其波峰到波谷的振幅(Vp.p)約1.5 μV。

English Abstract

This work introduces the method of variable thickness bridges (VTB) for fabricating high-Tc Josephson junctions and DC SQUIDs. Focused Ion Beam (FIB) is used to control the thickness of the junction under a nanometer. The region that links the two electrodes exhibits the weak link effect. YBa2Cu3O7-X (YBCO) VTBs were fabricated with widths of 1 - 3 μm and a thickness of 150 nm using the standard techniques of photolithography and Ar+ ion milling. The thickness of the junctions was maintained between 40 and 90 nm. When the thickness of the junction was close to 80 nm, the voltage-current curve revealed RSJ-like behavior at 77 K. The critical current vs. temperature curve satisfies the general equation, Ic∝(1-T/Tc)α, with α=2 near Tc and 1 at low temperature. Shapiro steps were observed in a single junction at frequencies from 3.02 to 14.64 GHz. The widths of the current steps revealed oscillatory behavior with irradiation intensities. The characteristics of DC SQUID magnetometer were also measured. The peak-to-peak voltage swing is about 1.5 μV for a single SQUID at 70 K.

Topic Category 理學院 > 奈米科學研究所
工程學 > 工程學總論
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Times Cited
  1. 蘇于宗(2012)。利用聚焦離子束製作不同厚度釔鋇銅氧微橋的微結構與電性分析。中興大學物理學系所學位論文。2012。1-69。