Date of Award

6-2023

Document Type

Dissertation

Degree Name

Ph.D.

Organizational Unit

College of Natural Science and Mathematics, Physics and Astronomy

First Advisor

Barry L. Zink

Second Advisor

Brian W. Michel

Third Advisor

Mark E. Siemens

Fourth Advisor

Davor Balzar

Keywords

Carbon nanotube, Characterization, Magnetic materials, Magnetism, Microcalorimetry, Wiedemann-Franz violation

Abstract

Modern fabrication and growth techniques allow for the development of increasingly smaller and more complex solid state structures, the characterization of which require highly specialized measurement platforms. In this dissertation I present the development of techniques and instrumentation used in magnetic, thermal, and electrical property measurements of thin films and nanostructures. The understanding of trapped-flux induced artifacts in SQUID magnetometry of large paramagnetic substrates allows for the resolution of increasingly small moments. Using these methods, the antiferromagnetic coupling of the interface between a Y3Fe5O12 film and Gd3Ga5O12substrate is quantitatively characterized, along with a number of other thin films. The use of custom fabricated silicon-nitride membrane thermal isolation platforms for temperature-dependent measurements is then presented for in-plane thermal conductivity, electrical conductivity, and thermopower of thin films. The size- and temperature-dependent properties of two types of semiconducting single-walled carbon nanotube thin films deposited and measured on these platforms reveal differing phonon contributions to thermal conductivity, and the interaction of dopant molecules and phonon transport in the disordered nanotube networks is explored. Experimental techniques for studying freestanding nanotube films is then presented, revealing a largely phonon-driven thermal conductivity that is greatly decreased by the introduction of phonon scattering sites. Next, time-dependent measurements on the suspended micromachined platforms was developed to allow for thermal detection of tiny depositions of energy from chemical reactions or physical processes in nanoscale systems. These experiments show our platforms have promise for open-chamber calorimetry of viral detection, and were expanded to include heat capacity into our suite of precision in-situ thermal measurements. Finally, copper thin films fabricated for heat capacity calibration are characterized and show a sharp reduction in thermal conductivity that ’violates’ the Wiedemann-Franz law.

Copyright Date

6-2023

Copyright Statement / License for Reuse

All Rights Reserved
All Rights Reserved.

Publication Statement

Copyright is held by the author. User is responsible for all copyright compliance.

Rights Holder

Michael J. M. Roos

Provenance

Received from ProQuest

File Format

application/pdf

Language

English (eng)

Extent

149 pgs

File Size

26.6 MB

Discipline

Condensed matter physics, Physics, Materials science

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