Full metadata
Title
Effect of helium ion irradiation on the tunneling behavior in niobium/aluminum/aluminum oxide/niobium Josephson junctions
Description
The study of high energy particle irradiation effect on Josephson junction tri-layers is relevant to applications in space and radioactive environments. It also allows us to investigate the influence of defects and interfacial intermixing on the junction electrical characteristics. In this work, we studied the influence of 2MeV Helium ion irradiation with doses up to 5.2×1016 ions/cm2 on the tunneling behavior of Nb/Al/AlOx/Nb Josephson junctions. Structural and analytical TEM characterization, combined with SRIM modeling, indicates that over 4nm of intermixing occurred at the interfaces. EDX analysis after irradiation, suggests that the Al and O compositions from the barrier are collectively distributed together over a few nanometers. Surprisingly, the IV characteristics were largely unchanged. The normal resistance, Rn, increased slightly (<20%) after the initial dose of 3.5×1015 ions/cm2 and remained constant after that. This suggests that tunnel barrier electrical properties were not affected much, despite the significant changes in the chemical distribution of the barrier's Al and O shown in SRIM modeling and TEM pictures. The onset of quasi-particle current, sum of energy gaps (2Δ), dropped systematically from 2.8meV to 2.6meV with increasing dosage. Similarly, the temperature onset of the Josephson current dropped from 9.2K to 9.0K. This suggests that the order parameter at the barrier interface has decreased as a result of a reduced mean free path in the Al proximity layer and a reduction in the transition temperature of the Nb electrode near the barrier. The dependence of Josephson current on the magnetic field and temperature does not change significantly with irradiation, suggesting that intermixing into the Nb electrode is significantly less than the penetration depth.
Date Created
2012
Contributors
- Zhang, Tiantian (Author)
- Newman, Nathan (Thesis advisor)
- Rowell, John M (Committee member)
- Singh, Rakesh K. (Committee member)
- Chamberlin, Ralph (Committee member)
- Wang, Robert (Committee member)
- Arizona State University (Publisher)
Topical Subject
Resource Type
Extent
xii, 76 p. : ill. (some col.)
Language
Copyright Statement
In Copyright
Primary Member of
Peer-reviewed
No
Open Access
No
Handle
https://hdl.handle.net/2286/R.I.15148
Statement of Responsibility
by Tiantian Zhang
Description Source
Retrieved on July 23, 2013
Level of coding
full
Note
Partial requirement for: M.S., Arizona State University, 2012
Note type
thesis
Includes bibliographical references (p. 72-76)
Note type
bibliography
Field of study: Materials science and engineering
System Created
- 2012-08-24 06:31:04
System Modified
- 2021-08-30 01:45:22
- 2 years 8 months ago
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