Current-voltage characteristics of Nb-carbon-Nb junctions

I. P. Nevirkovets, Serhii Shafraniuk, O. Chernyashevskyy, N. Masilamani, J. B. Ketterson

Research output: Contribution to journalArticlepeer-review


We report on properties of Nb(/Ti)-carbon-(Ti/)Nb junctions fabricated on graphite flakes using e-beam lithography. The devices were characterized at temperatures above 1.8 K where a Josephson current was not observed, but the differential conductivity revealed features below the critical temperature of Nb, and overall metallic conductivity, in spite of a high-junctions resistance. Since the conductivity of graphite along the planes is essentially two-dimensional (2D), we use a theoretical model developed for metal/graphene junctions for interpretation of the results. The model involves two very different graphene "access" lengths. The shorter length characterizes ordinary tunneling between the three-dimensional Nb(/Ti) electrode and 2D graphene, while the second, much longer length, is associated with the Andreev reflections (AR) inside the junction and involves also " reflectionless" AR processes. The relevant transmission factors are small in the first case and much larger in the second, which explains the apparent contradiction of the observed behaviors.

Original languageEnglish (US)
Pages (from-to)250-258
Number of pages9
JournalFizika Nizkikh Temperatur
Issue number3
StatePublished - Jan 1 2014


  • Andreev reflection
  • Carbon
  • Graphene
  • Josephson effect
  • Superconductivity
  • Tunnel junctions

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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