在超導材料中，高溫超導中造成庫伯電子對形成的機制一直是一項令人好奇的題目。而近期的研究中，表明了在銅氧化物高溫超導(Cuprate)中，電子對的結合可能是由於其中超導平面的d-wave對稱性所引起的，因此為了證實其存在，先前的研究將釔鋇銅氧(YBa2Cu3O7-x)薄膜生長於雙晶向基板上，以使得在其介面產生約瑟芬現象(Josephson Junction)。透過研究約瑟芬現象的臨界電流和晶向的偏轉角度，可以證實d-wave對稱性在超導體內部對電子對的結合佔有重要的地位。
在我們的研究中，運用了脈衝雷射沉積法的技術成長高溫超導薄膜，並且也透過濕式蝕刻轉移(Freestanding)的技術將薄膜轉移至其他基板上，使得生長於其上之YBCO擁有不同晶向。並利用國家同步輻射中心(NSRRC)提供的高解析X射線(X-Ray Diffraction & X-Ray Linear Dichroism)來確認轉移前及轉移後的薄膜對成長於其上之YBCO並無造成明顯結構差異，且在其a軸及b軸有較高吸收強度，符合d-wave超導體之預測。最後再透過電性量測來確認其介面之臨界電流，以佐證這類轉移薄膜能在晶向介面呈現d-wave超導體特有的晶向介面約瑟芬效應。

How electrons mate each other and form Cooper pairs in high temperature superconductor (HTS) is a question bothering scientists since 1950s. According to previous studies, several researchers mentioned that Cooper pairs may be caused by the d-wave symmetry in the superconducting plane in Cuprate. To prove the existence of d-wave symmetry, they grew YBa2Cu4O7-x(YBCO) thin films on bi-crystal substrates and observed the Josephson effect happened at the grain boundary (GB). Through the experiments to understand the relation between critical currents and twist angles in Josephson junctions (JJ), they unveiled the d-wave symmetry domains in superconductors served as a key to lead electrons pairing to each other.
In our research, we made a special Josephson junction which was formed by a bi-crystal grain boundary composed with two different crystalline oriented epitaxial HTS YBCO thin films, (001)- and (101)-oriented. And trying to confirm if the mechanism of d-wave symmetry mentioned in previous studies happens in our junctions. Meanwhile, we also expected to find out novel properties and reveal the corresponding mechanism behind.
These special epitaxial thin films were carried out by pulsed laser deposition (PLD) and freestanding technique. We analyzed both the crystal structure of two orientation, namely the as-grown site YBCO and the freestanding site YBCO, by using the high resolution x-ray diffraction (HRXRD) and soft x-ray absorption spectrum (XAS) . The transport behavior in the junction was detected and analyzed through the current-voltage measurement under the variant applied magnetic field. To further explore the physical properties in the special Josephson junctions, we changed the twist angle between two orientation sites in lateral direction and observed the critical currents in different angles respectively. Thus, we could realize how twist angles affect the transport behavior in the grain boundary of two oriented YBCO.
We discovered that the transport behavior of this special bi-crystal boundary has the same performance as Josephson junctions mentioned in previous studies noticed that the magnitudes of critical currents present Fraunhofer pattern as the changing of external B-field. These results gave a different perspective to control the phase transition behavior in superconductors and provide a new option to tune carriers transport behavior in superconductive complex oxides system.

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