Date of Award

2012-01-01

Degree Name

Doctor of Philosophy

Department

Material Science and Engineering

Advisor(s)

Felicia S. Manciu

Abstract

Tungsten oxide (WO3) is important and well-studied in materials science, particularly for sensor applications. In this research work, we consider the innovation of adding Ti to thin films of this material. Since the characteristics of any such material are strongly dependent on the conditions and methods used in its deposition, the main objective of this project is to provide a detailed spectroscopic characterization by Raman scattering, infrared absorption, and X-ray photoelectron spectroscopy (XPS) of WO3 and of W0.95Ti0.05O3. This characterization will be based on comparison of the morphology and composition of WO3-based thin films, grown by radio frequency magnetron reactive sputtering at substrate temperatures varied from room temperature (RT) to 500 ºC. In the W0.95Ti0.05O3 thin films, our Raman data reveal a phase transformation from a monoclinic WO3 structure to an orthorhombic or tetragonal configuration, based on peak shifts of WO3 W-O-W stretching modes from 806 and 711 cm-1, to 793 and 690 cm-1, respectively. In addition, Ti-doped WO3 films require higher growth temperatures to attain crystalline microstructure than do pure WO3 films. XPS data indicate a reduced WO3-x stoichiometry at the surface of the doped material, with W6+ and W5+ tungsten oxidation states present. This observation could easily be related to the existence of a different structural phase of this material,

corroborating the Raman measurements.

Language

en

Provenance

Received from ProQuest

File Size

72 pages

File Format

application/pdf

Rights Holder

James Heyward Howard

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