Berlin 2005 – scientific programme

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TT: Tiefe Temperaturen

TT 10: Superconductivity - Tunneling, Josephson Junctions, SQUIDs

TT 10.8: Talk

Saturday, March 5, 2005, 10:15–10:30, TU H104

Epitaxial growth of Al/AlOx/Al trilayers for Josephson junction fabrication — •J. Eroms, A.H. Verbruggen, C.J.P.M. Harmans, A.v.d. Enden, P.F.A. Alkemade, A.R.H.F. Ettema, H.W. Zandbergen, and J.E. Mooij — Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, The Netherlands

Superconducting qubit circuits are mainly built from aluminum based Josephson junctions fabricated by shadow evaporation or in a trilayer process. The aluminum films are polycrystalline in both cases. Charge noise and critical current fluctuations limit the performance of present qubits made from those devices. To achieve a defect free barrier, we explore epitaxial aluminum films as a base material for Josephson junctions. We grow Al/AlOx/Al trilayers on Si (111) wafers in a molecular beam epitaxy system. The films are characterized in situ with RHEED and after growth with high-resolution TEM, Kikuchi backscattering and X-ray reflectivity measurements. The bottom Al layer grows epitaxially on the Si subtrate, the oxide barrier appears amorphous, but very smooth, and the top Al layer is polycrystalline, but with Al (111) planes still parallel to the Si (111) planes.