Abstract

In this work, tungsten oxide thin films were fabricated using magnetron sputter deposition and electron beam evaporation under varying oxygen conditions to produce a range of stoichiometries, including substoichiometric compositions near WO₂.₇. The primary goal was to evaluate how reliably X-ray photoelectron spectroscopy (XPS) can quantify the stoichiometry of WOₓ thin films, determine how deposition conditions influence measured composition and oxidation states, and assess how argon ion sputtering, used for surface cleaning, alters tungsten oxidation states and affects XPS based stoichiometry. The films were analyzed using XPS under ultra-high vacuum conditions. Survey spectra were used to identify elemental composition, while high-resolution spectra of the W 4f, O 1s, and C 1s regions were used to evaluate oxidation states, oxygen content, and carbon contamination. Surface contamination was addressed using wet chemical treatment and in situ argon ion sputtering. Spectra were processed using C 1s energy calibration, Shirley background subtraction, relative sensitivity factor correction, and pseudo-Voigt peak fitting. Deconvolution of the W 4f region revealed the presence of multiple oxidation states, including W⁶⁺, W⁵⁺, and W⁴⁺. The results demonstrate ion sputtering effectively reduces adventitious carbon but also induces preferential oxygen removal, leading to systematic reduction of tungsten oxidation states and a decrease in measured oxygen content. In initial samples, carbon removal was most significant during early sputtering cycles, after which the carbon signal plateaued in some samples, suggesting the presence of internal or incorporated carbon. A later film, Sample D Slot 10, showed improved behavior, reaching very low carbon levels after a single ion etch while retaining concentrations consistent with WO₂.₇. These findings highlight a fundamental tradeoff between contamination removal and chemical modification and establish a framework for interpreting XPS measurements of nonstoichiometric tungsten oxide thin films.

Publication Date

7-2026

Document Type

Thesis

Student Type

Graduate

Degree Name

Materials Science and Engineering (MS)

Department, Program, or Center

Chemistry and Materials Science, School of

College

College of Science

Advisor

Michael Pierce

Advisor/Committee Member

Pratik Dholabhai

Advisor/Committee Member

Parsian Mohseni

Campus

RIT – Main Campus

Plan Codes

MSENG-MS

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