Title

Uniformity of VO2 Phase Change Material (PCM) Thin Films Produced by Thermal Oxidation of Vanadium

Date of Award

2021

Degree Name

M.S. in Chemical and Materials Engineering

Department

Department of Chemical and Materials Engineering

Advisor/Chair

Andrew Sarangan

Abstract

VO2 is a type of phase change material (PCM) that can switch between a metallic state and a semiconducting state at a temperature of around 68┬░C. This produces a large change in electrical resistance (almost three orders of magnitude) and large optical changes. Since this phase change occurs close to room temperature, VO2 has a large number of potential applications, such as thermally activated switches, optical modulators and optical limiters. Due to the multiple oxidation states of vanadium, VO2 thin films are typically difficult to produce. Traditionally, they are produced by reactive physical vapor deposition on heated substrates. In our research group, we have developed a different method where VO2 thin films are fabricated by thermal oxidation of PVD-deposited metallic vanadium films. Due to the high reactivity of vanadium, even small changes in the oxidation conditions will result in significant variations in the oxide films. In this thesis, we have examined the uniformity of VO2 films using stylus profiling, SEM, and 4-point probe measurements. The thickness expansion of the films due to oxidation was calculated and verified against experimental data. We also characterized the temperature profile inside the oxidation furnace. In addition, following an approach similar to the thermal oxidation of silicon, a vanadium oxidation model combining multiple oxidation states has been proposed and developed.

Keywords

Materials Science, Engineering, Optics, phase change materials, thin films, VO2, thermal oxidation, uniformity measurement, vanadium oxidation model

Rights Statement

Copyright 2021, author

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