Superconducting transition temperature of niobium/graphite bilayers

• Published in: Physica. C, Superconductivity Superconductivity, 2004-12, Vol.417 (1), p.58-62
• Main Authors: Kubo, Toshiharu, Ohashi, Yoshiko F., Kinoshita, Takeshi
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Graphite; Multilayers, superlattices , heterostructures; Niobium; Physics; Proximity effect; Superconducting films and low-dimensional structures; Superconducting materials (excluding high-tc compounds); Superconductivity; Superconductor; Transition temperature
• ISSN: 0921-4534; 1873-2143
• DOI: 10.1016/j.physc.2004.10.007

The superconducting proximity effect in niobium/graphite bilayers was studied. Thin graphite films of various thickness ranging from around 20–160 nm were prepared by cleaving a kish graphite (KG). For making a specimen, niobium (Nb) of 40 nm in thickness was deposited on a KG film and a quartz glass substrate simultaneously using electron-beam evaporation method. Each resistance of Nb and Nb/KG films was measured at the same time, and transition temperature of Nb film ( T C S ) and Nb/KG film ( T C ∗ ) on the same substrate was obtained. The ratio of T C ∗ to T C S ( T C ∗ / T C S ) showed a periodic characteristic with KG film thickness. Furthermore, the peak values of the ratio exceeded 1.00. This result suggests that the electron correlation at Nb/KG interface changes depending on KG film thickness because of the interference of electrons as wave in the KG film.