The fabrication of PBCO buffered step-edge Josephson junctions

[摘要] 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 muchneeded improvements. These improvements included a newly optimised photolithographyprocess, the incorporation of a three-gridded extraction system into the in-house argonion mill as well as alterations to the Pulsed Laser Deposition (PLD) system to improvethin film quality. These process modifications finally allowed for the fabrication of novelPrBa2Cu3O7−δ buffered step-edge junctions. These junctions were tested for dc and acJosephson effects and displayed IcRn products of 1.5 mV at 55 K as well as well-definedShapiro steps.A second objective was to introduce a high quality thin film deposition system that couldproduce smooth superconducting films for use in filters and multilayer technology. AnInverted Cylindrical Magnetron system was built and optimised to grow YBa2Cu3O7−δthin films on MgO (001) substrates. A complete optimisation process of these films arepresented by utilising several growth and electrical characterisation methods such as XRD,RBS and AFM.

[发布机构] Stellenbosch University