The fabrication of PBCO buffered step-edge Josephson junctions

Van Staden, Wynand Fourie
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A major challenge in the design and operation of High Temperature Superconducting (HTS) devices is the fabrication of reproducible Josephson junctions with good IcRn products. One objective of this thesis was to fabricate successfully HTS step-edge junctions. This objective necessitated a critical evaluation of the available facilities to provide much needed improvements. These improvements included a newly optimised photolithography process, the incorporation of a three-gridded extraction system into the in-house argon ion mill as well as alterations to the Pulsed Laser Deposition (PLD) system to improve thin film quality. These process modifications finally allowed for the fabrication of novel PrBa2Cu3O7−δ buffered step-edge junctions. These junctions were tested for dc and ac Josephson effects and displayed IcRn products of 1.5 mV at 55 K as well as well-defined Shapiro steps. A second objective was to introduce a high quality thin film deposition system that could produce smooth superconducting films for use in filters and multilayer technology. An Inverted Cylindrical Magnetron system was built and optimised to grow YBa2Cu3O7−δ thin films on MgO (001) substrates. A complete optimisation process of these films are presented by utilising several growth and electrical characterisation methods such as XRD, RBS and AFM.
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2007.
Dissertations -- Electronic engineering, Theses -- Electronic engineering, Josephson junctions, Superconductivity, Photolithography