Fabrication and Tunneling Characteristics ofYBCO / Au / Pb Josephson Junction

• Main Authors: Shin-Yi Wu, 吳欣怡
• Other Authors: Tzay-Shing Lai
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/47464686442618713355

碩士 === 中原大學 === 應用物理研究所 === 91 === The main work of this thesis consists of【1】epitaxial growth of YBCO superconducting thin films by RF sputtering .【2】 fabrication and characteristics of YBCO / Au / Pb Josephson junction with counter electrode Pb by evaporation .【3】physical properties of non-uniform Josephson junctions in applied magnetic field . For the first part , we used MgO as our substrate . By the comparison of the critical temperature ( TC ) and surface roughness , we obtained the optimal parameters of our YBCO films . We simulated the relation between the critical current ( IC )and applied magnetic field ( B ) for a non-uniform Josephson junction and made comparison with our experimental results . Secondly , for the study of the characteristics of Josephson junction , we fabricated YBCO / Au / Pb sandwich - type Josephson junction and conducted the measurements of voltage - current ( V–I ) relation ; critical current–magnetic field ( IC - B ) relation ; the critical current - temperature ( IC -T ) relation and conductance–voltage ( G-V ) relation . Our observations showed that (1) the V–I curves of our Josephson junctions fabricated by wet-etching photolithography agree well with the prediction of RSJ model . (2) the magnetic field - varied V–I curves showed that the critical current - magnetic field relation exhibited a conventional Fraunhofer diffraction pattern with a global maximun of IC at B = 0 . (3) the temperature - varied V–I curves show that the critical current decreases as the temperature increases . (4) the G–V curve suggested that YBCO is superconductor with s–wave pairing symmetry , with no indication of d–wave pairing . Existing reports reveal that Josephson junctions fabricated with the method we used could not exhibit all the pairing symmetry of YBCO。