Year

2023

Season

Fall

Paper Type

Master's Thesis

College

College of Arts and Sciences

Degree Name

Master of Science in Material Science & Engineering (MS)

Department

Physics

NACO controlled Corporate Body

University of North Florida. Department of Physics

Committee Chairperson

Daniel Santavicca

Second Advisor

Maitri Warusawithana

Rights Statement

http://rightsstatements.org/vocab/InC/1.0/

Third Advisor

Steve Stagon

Abstract

This thesis involves the fabrication and characterization of devices made from two different superconducting materials: yttrium barium copper oxide (YBCO), a high-TC complex oxide, and niobium nitride (NbN), a low-TC transition metal nitride. Both types of devices are fabricated on strontium titanate substrates, which provides a good lattice match to YBCO and also an extremely large permittivity at low temperature. We demonstrate that wet etching of YBCO thin films via bromine can be a viable microfrabriation technique for the material. Using approximately 35 nm thick epitaxially grown YBCO on an STO substrate, we were able to fabricate YBCO “microwires” with widths of 5 μm and 50 μm. These wires had a superconducting critical temperature (TC) of 86 K and a critical current density of 1 × 1011 A/m2 at low temperature, indicating that our fabrication process yields wires with electrical properties that are close to that of the bulk material. We have also developed impedance-matched lowloss microwave resonators using high kinetic inductance NbN nanowires on a substrate consisting of 100 nm of epitaxial STO on a 0.5 mm thick lanthanum aluminate (LAO) substrate. Comparing the measured transmission coefficient to numerical simulations, we were able to determine the dielectric constant of the STO film and determined it to be ϵ = 590 with an upper bound on the STO loss tangent of tan δ = 5 × 10−4 at 4.5 K. These devices demonstrate the potential for combining high-inductance superconducting nanowires with high-permittivity substrates to realize impedance-matched devices with dramatic spatial compression of the signal wavelength.

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