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Event Number 2669

  Monday, May 21st, 2012

R. G. Herb Condensed Matter Seminar
Advancements in epitaxial trilayer growth utilizing Nb/Re bilayers on sapphire
Time: 12:00 pm
Place: 5310 Chamberlin
Speaker: Paul Welander, MIT Lincoln Laboratory
Abstract: A new approach to all-epitaxial "trilayer" growth has been developed for superconducting Josephson junction applications, utilizing a multi-layer stack which includes buffer layers between the electrodes and the tunnel-barrier. These buffer layers serve as both diffusion barriers and structural transitions between dissimilar materials, and if kept thin (~ 10 nm) proximity effects with the electrodes dominate and the entire structure behaves like an SIS trilayer. This course has been charted due to advancements in the hetero-epitaxial growth of Re (0001) layers on Nb (110) surfaces by MBE. Thick Nb (110) films were grown on A-plane sapphire and found to be single-crystal and atomically smooth (rms roughness ~ 0.2-0.3 nm). Thin Re (0001) overlayers retained this atomically smooth surface morphology, providing an ideal template onto which an ultra-thin Al2O3 layer could be grown. RHEED analysis also indicated that any misfit strain in the Re layer had nearly diminished within the first 10 nm of deposition. These materials have been incorporated into all-epitaxial Nb/Re/Al2O3/Al/Nb trilayers. Both the materials analysis and electrical characterization will be reported.
Host: Rzchowski
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