Year

2021

Degree Name

Doctor of Philosophy

Department

School of Physics

Abstract

Continual improvements to superconducting devices is a fundamental requirement for optimised operation. Using a variety of contrastingly shaped, relatively large 2–5 µm fully (antidot-AD) and partially etched (blind) holes, the Jc of YBCO thin films has been effectively increased. The enhancement to Jc is present within the relatively narrow band of wall surfaces of ADs, independent of whether patterns were ADs or the blind AD type. Independence of AD types indicates that enhancement is insensitive whether magnetic flux is inside the ADs, or vortices are inside the blind holes. Within this AD wall surface band region a clear shape dependence also emerges. This finding may also provide a guide for superconducting devices requiring maximal Jc and reduced associated vortex movement noise.

Continuing the trend of increasing the Jc of YBCO thin films via vortex pinning, a novel technique was proposed and implemented. The new flux pinning technique involves ion beam etching specific locations on the substrate prior to deposition, as opposed to etching of ADs into the YBCO surface. Jc enhancements of >40% were obtained at zero field and 85K relative to an unpatterned substrate film. This new substrate nanoengineering technique is promising for flux trapping of superconducting devices, particularly because an increase to critical current (Ic) also occurs. Further optimisation of depth, size, and shape of the patterns is expected to produce further improvements to Jc.

FoR codes (2008)

0204 CONDENSED MATTER PHYSICS

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.