Thermochromic Properties of VO2 + ZrO2 Based Bi- and Triple- Layer Thin Films for Optical Applications
Date
2024-09-17
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
0009-0008-3905-7633
Type
Thesis
Degree Level
Masters
Abstract
Vanadium dioxide (VO2) films have shown usefulness as a part of optoelectrical devices due to
rapid reversible phase transition which sees large changes in both optical and electric properties.
This transition sees insulating monoclinic structure films with high optical transmittance and
electrical resistivity change at 69 °C to metallic rutile structure which has low optical
transmittance and electrical resistivity. Potential utilizations of VO2 films include smart
windows, optical and electrical switching, and smart radiators for small satellites. Application
designs regularly require additional oxide layers. Zirconium dioxide shows promise as an
additional oxide layer due to high robustness, and compatible optical/structural properties. Due
to vanadium having a high number of oxidative states, VO2 films are sensitive to oxidation and
are difficult to manufacture at a high quality.
In this current study, three different layered designs that include VO2 and ZrO2 layers were
synthesized by reactive magnetron sputtering on Si and sapphire substrates. Layer designs
include two bi-layers, which have ZrO2 as a base layer with VO2 deposited on top (ZrO2/VO2),
and the reverse with ZrO2 deposited on top of a VO2 layer (VO2/ZrO2). Two triple-layer designs
with a VO2 layer between ZrO2 layers (ZrO2/VO2/ZrO2) were deposited with different top layer
deposition temperatures of 500 °C and 650 °C. The effect of these different layer designs on the
structure of these films showed oxidization of VO2 films when ZrO2 is deposited as a top layer in
Raman spectroscopy and SEM testing. These films showed incomplete transitions upon heating
but still may be useable in applications that do not require a complete transition such as smart
windows. ZrO2/VO2 samples showed no oxidization and had sharp, complete transitions in
optical testing. The effect of this structural change was found to outweigh changes in roughness
found in these samples. These results suggest that designs for switching that require full
transition should use VO2 deposited as a top layer deposited on ZrO2.
Description
Keywords
Vanadium Dioxide, Phase transition, Zirconium Oxide, VO2, ZrO2, Thin Films,
Citation
Degree
Master of Science (M.Sc.)
Department
Mechanical Engineering
Program
Mechanical Engineering
Advisor
Committee
Yang, Qiaoqin;Odeshi, Akindele;Evitts, Richard