Superconducting transition temperature of niobium/graphite bilayers

Toshiharu Kubo; Yoshiko F. Ohashi; Takeshi Kinoshita

doi:10.1016/j.physc.2004.10.007

Superconducting transition temperature of niobium/graphite bilayers

Toshiharu Kubo, Yoshiko F. Ohashi, Takeshi Kinoshita

Department of Electronics and Electrical Engineering

Research output: Contribution to journal › Article › peer-review

4 Citations (Scopus)

Abstract

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^S_C) and Nb/KG film (T* _C) on the same substrate was obtained. The ratio of T* _C to T^S_C (T*_C/T ^S_C) 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.

Original language	English
Pages (from-to)	58-62
Number of pages	5
Journal	Physica C: Superconductivity and its applications
Volume	417
Issue number	1-2
DOIs	https://doi.org/10.1016/j.physc.2004.10.007
Publication status	Published - 2004 Dec 15

Keywords

Graphite
Niobium
Proximity effect
Superconductor
Transition temperature

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials
Condensed Matter Physics
Energy Engineering and Power Technology
Electrical and Electronic Engineering

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10.1016/j.physc.2004.10.007

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title = "Superconducting transition temperature of niobium/graphite bilayers",

abstract = "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 (TSC) and Nb/KG film (T* C) on the same substrate was obtained. The ratio of T* C to TSC (T*C/T SC) 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.",

keywords = "Graphite, Niobium, Proximity effect, Superconductor, Transition temperature",

author = "Toshiharu Kubo and Ohashi, {Yoshiko F.} and Takeshi Kinoshita",

note = "Funding Information: We are grateful to Professor Y. Hishiyama of Musashi Institute of Technology for kindly supplying a precious KG crystal. We would thank K. Kitamura for his help in evaporation of Nb films and also thank Professor S. Anzai for valuable discussions. A part of this work was supported by Keio Gijuku Academic Development Funds.",

year = "2004",

month = dec,

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doi = "10.1016/j.physc.2004.10.007",

language = "English",

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journal = "Physica C: Superconductivity and its applications",

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TY - JOUR

T1 - Superconducting transition temperature of niobium/graphite bilayers

AU - Kubo, Toshiharu

AU - Ohashi, Yoshiko F.

AU - Kinoshita, Takeshi

N1 - Funding Information: We are grateful to Professor Y. Hishiyama of Musashi Institute of Technology for kindly supplying a precious KG crystal. We would thank K. Kitamura for his help in evaporation of Nb films and also thank Professor S. Anzai for valuable discussions. A part of this work was supported by Keio Gijuku Academic Development Funds.

PY - 2004/12/15

Y1 - 2004/12/15

N2 - 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 (TSC) and Nb/KG film (T* C) on the same substrate was obtained. The ratio of T* C to TSC (T*C/T SC) 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.

AB - 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 (TSC) and Nb/KG film (T* C) on the same substrate was obtained. The ratio of T* C to TSC (T*C/T SC) 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.

KW - Graphite

KW - Niobium

KW - Proximity effect

KW - Superconductor

KW - Transition temperature

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Superconducting transition temperature of niobium/graphite bilayers

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