高溫超導體/石墨烯約瑟芬元件製作與傳輸特性研究

Abstract

本篇論文主題是高溫超導體與石墨烯約瑟芬接面 (Josephson Junction) 的製作與其電子傳輸特性的研究。想法來源為低溫超導體與石墨烯之間的安德烈夫反射現象 (Andreev reflection) 與鄰近效應 (proximity effect)，而我們則是選用高溫超導體 (EBCO) 與石墨烯製作出約瑟芬接面來試圖觀察上述的效應，並了解超導載子在接面中穿隧的物理機制，更希望能就藉由這個研究製作出更好的約瑟芬接面。

論文的另一個部分是研究外延石墨烯 (Epitaxial graphene) 的傳輸特性，我們觀察到絕緣態與量子霍爾態的相變與弱局部化 (Weak localization) 的效應。並且成功的將電子-電子散射 (electron-electron scattering) 、電子-聲子散射 (electron-phonon scattering)這兩種難以個別研究的散射機制藉由電子加熱效應 (current heating effect) 將其個別探討。 最後，我們的實驗成功製作出高溫超導與石墨烯的約瑟芬接面，而且觀察到在高溫超導體與石墨稀接面發生安德烈夫反射現象的證據。這是目前別人尚未做過的嘗試。期望在未來有更進一步的發展性，及前瞻性的應用。

In this thesis, the electron transport properties and the fabrication of Josephson junction in a hybrid high-temperature superconductor and graphene were investigated. The idea of adopting high-temperature superconductor, EuBaCuO (EBCO), and graphene derived from the Andreev reflection and proximity effect observed between the interface of the low-temperature superconductor and graphene; attempting to have a comprehensive picture of the aforementioned effects and the fundamental properties of the superconducting carriers in the Josephson junction in a variety of superconductors. Besides what we mentioned in the previous paragraph, the rest of this thesis was dedicated to the study of the electrons transport properties in the epitaxial graphene. The behaviors of the insulator-quantum Hall transition and weak localization in the epitaxial graphene were observed in this study. Moreover, our experimental results suggested that the electron heating effect is a powerful tool for studying two scattering properties which are difficult to study independently and physical phenomena in two-dimensional systems or nanostructures. Finally, we successfully demonstrated the fabrication of high-temperature superconducting/graphene Josephson junction and evidences responsible for Andreev reflection phenomenon observed in the high-temperature superconductors/graphene Josephson junction. The results of this unprecedented materials combination shed a light on the future development of its cutting-edge applications.