Date of Award

5-2024

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Physics

Committee Chair/Advisor

Kasra Sardashti

Committee Member

Chad Sosolik

Committee Member

Joan Marler

Abstract

Superconducting qubits have emerged as a promising platform for realizing error-corrected quantum computing. Reaching the minimum threshold for error correction requires scaling the number of qubits well beyond the current numbers while improving their coherence and minimizing their crosstalk. Such daunting demands require groundbreaking innovations in the design of superconducting quantum circuits as well as in engineering the materials integrated into the devices. This thesis explores materials solutions for two different scalability problems: 1) crosstalk and 2) loss due to surface oxidation. The crosstalk is addressed by making voltage-tunable superconductor-semiconductor Josephson junctions (JJs). For the loss due to surface oxidation, we explore ruthenium (Ru) as a capping layer that can inhibit surface oxidation rates for the underlying niobium (Nb) or tantalum (Ta) thin films. The thesis starts with an introduction to superconductivity and how it led to superconducting quantum bits. Chapter 2 discusses the experimental tools utilized for the fabrication and characterization of thin films and devices. Chapter 3 focuses on Nb/Ge interfaces for hybrid superconductor-semiconductor devices. In Chapter 4 we discuss Ru thin films as a capping layer for superconducting quantum circuits. We analyze the oxide formation on Ru thin film surfaces and characterize the electronic transport properties. The thesis concludes with the future direction for the two parts of this study including integration of our chemically-abrupt Nb/Ge interfaces into voltage-tunable JJs and the application of our thin-film superconducting Ru capping layers as passivation layers in superconducting resonators.

Available for download on Saturday, May 31, 2025

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