Fabrication of Vanadium Dioxide Thin Films and their Structural, Optical and Electrical Characterization for Optoelectronic Applications
Date
2023-02-23
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
0000-0001-6171-1832
Type
Thesis
Degree Level
Doctoral
Abstract
Vanadium dioxide (VO2) is a transition metal oxide that is well known for its metal-to-insulator phase transition (MIT). One of the most common forms of VO2 that has been generally studied is the thin film form. VO2 thin films are considered a strong candidate in various new-generation optical, electronic, and optoelectronic (photonic) applications. From the technology perspective, the fabrication of single-crystal VO2 thin films appears to be challenging. Up to now, research on the preparation of VO2 thin films has focused on employing different material fabrication techniques to produce high-quality VO2 thin films. The stoichiometry and quality of VO2 thin films strongly depend on the fabrication process. There is still a need to study the production of near-single-crystal, high-quality VO2 thin films and their structural, optical and electrical characterization. Secondly, the metal-to-insulator phase transition phenomenon in VO2 is a topical research field. The percolation theory has introduced some rigor in explaining the phase transition. This dissertation focuses on two aspects of research on VO2 thin films. The first aspect focuses on studying the effect of specific deposition parameters such as substrate biasing and substrate temperature on the quality of VO2 thin films. Also, the synthesis of high-quality VO2 thin films prepared on single-crystal silicon, quartz and sapphire substrates is investigated. The films are examined using various analysis techniques including Raman spectroscopy, scanning electron microscopy (SEM), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and energy-dispersive x-ray spectroscopy (EDS). The optical constants, namely the refractive index (n) and the extinction coefficient (K), and the optical bandgap (Eg) of the films are extracted using the Swanepoel and Manifacier techniques. The second aspect of this dissertation covers the application of percolation theory on the phase transition in VO2 thin films. Accordingly, the topology of conducting clusters during the IMT and MIT is investigated by means of optical and electrical switching in a high-quality VO2 thin film. Additionally, self-heating-induced electrical and optical switching in VO2 thin films prepared on sapphire substrates under constant applied current pulses has been studied. The difference in the two switching dynamics is explained by a simple model based on the percolation theory.
Description
Keywords
Vanadium dioxide thin films, metal-to-insulator phase transition, DC magnetron sputtering, structural, optical and electrical characterization, near-epitaxial growth, percolation theory, electrical and optical switching.
Citation
Degree
Doctor of Philosophy (Ph.D.)
Department
Electrical and Computer Engineering
Program
Electrical Engineering