Date of Award
Summer 2026
Language
English
Embargo Period
8-13-2026
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
College/School/Department
Department of Nanoscale Science and Engineering
Program
Nanoscale Engineering
First Advisor
Harabolos Efstathiadis
Committee Members
Iulian Gherasoiu, Menbing Huang, John Zeller, Higashiya Seiichiro
Keywords
Thin-film, Magnetron Sputtering, Vanadium Oxide, Temperature Coefficient of Resistance, Material Characterization, Electrical Characterization, Optical Studies, Nanoscale material
Subject Categories
Nanoscience and Nanotechnology | Semiconductor and Optical Materials
Abstract
This thesis details the development of multivalence-nanostructured vanadium oxide (VOₓ) thin films for uncooled microbolometer applications, with a systematic optimization of magnetron-sputtering parameters. The temperature coefficient of resistance (TCR), resistivity, and optical response of VOₓ thin-film sensing layers are controlled by valence composition, grain growth, and surface morphology. The primary goal was to achieve a high TCR with low resistivity to improve thermal detector performance.
Multivalent VOₓ thin films were deposited on silicon, SiO₂, and glass substrates using DC magnetron sputtering. Three key parameters were systematically varied: Ar:O₂ ratio (18:2 to 15:5), deposition time (60–120 minutes), and DC power (300W and 350W).
The films showed mixed valence states of V₂O₅ (V⁵⁺), VO₂ (V⁴⁺), and V₂O₃ (V³⁺) along with O/V ratios of ~1.5–3.0 and densities of 2.44–3.70 g cm⁻³, as confirmed by X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectroscopy (RBS).
While grain and morphological studies using AFM/SEM reveal Stranski–Krastanov growth at 300 W and Volmer–Weber growth at 350 W, surface roughness and grain size generally increase with time and oxygen fraction, with stress-induced re-nucleation observed at select conditions. Surface roughness ranged from 0.52- 7.4 nm with grain sizes varying from 10- 70 nm depending on deposition conditions.
Optical characterization (ellipsometry, UV–Vis/IR) confirmed thicknesses of 20–85 nm, refractive index n = 1.9–2.6, transmissions typically 65–73%, and reflectance red-shifts with increasing thickness and phase evolution.
Most significantly, electrical measurements demonstrated a TCR of -3.86% K⁻¹ at 300K, substantially exceeding the literature value of -1.9% K⁻¹. The optimized films deposited at Ar: O₂ ratio 16:4 with 350W DC power showed the most promising combination of high TCR and controlled resistivity.
Collectively, these results establish quantitative links between deposition parameters, growth mode, phase evolution, and key figures of merit for VOₓ bolometers. This work also establishes a foundation for integrating these nanostructured VOₓ films with carbon nanotubes and graphene for next-generation high-performance thermal detectors.
License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Recommended Citation
Chaudhary, Latika Susheel M., "High-TCR Multivalence Vanadium Oxide Thin-films From Deposition Parameter Control to Microbolometer Applications" (2026). Electronic Theses & Dissertations (2024 - present). 538.
https://scholarsarchive.library.albany.edu/etd/538