Application of the x-ray photoelectron spectroscopy for development of the niobium chemical mechanical process, photomodification of silicon for the field release mass spectrometer, and analysis of the multifunctional oxide heterostructures
Katherine S. Ziemer
Daniel D. Burkey, Shashi Krishna Murthy, Sinan Muftu
Date of Award
Master of Science
Department or Academic Unit
College of Engineering. Department of Chemical Engineering.
Chemical engineering, X-ray photoelectron spectroscopy (XPS)
X-ray photoelectron spectroscopy, Surfaces (Technology), Electronic measurements
X-ray photoelectron spectroscopy (XPS) provides information about the elemental chemical composition of a surface and the bonding states of those elements. This information is critical to diverse applications where the surface of the material determines its functionality such as tuned catalysts, engineered polymer coatings, and nanoelectronic heterostructures. For this thesis, XPS has been applied in both traditional and novel ways to niobium surface polishing, silicon surface modification, and electronic structure measurement. The current method for fabricating niobium superconducting cavities produces rough and defective surfaces. A proof-of-concept project to develop a niobium Chemical Mechanical Polishing (CMP) process used XPS to monitor surface composition and structure under varying CMP parameters. XPS confirmed rapid oxidation of the niobium with a self-limiting surface oxide of 5.0±0.8 nm. CMP surface effects were explored and a smooth (24 nm average roughness) niobium wafer with an ordered surface was produced. Current methods of detecting complex airborne toxins such as anthrax are time consuming and often give false positives . A modified field release mass spectrometer (FRMS) will enable specific and selective real-time detection of air toxins through utilization of the modified silicon surfaces for the capture and release of these analytes. Photomodification of the silicon surface with undecylenic acid resulted in 42±1 % monolayer coverage as determined from the XPS and angle resolved XPS (ARXPS) data using an adapted method from Haber et al. in . Carbon contamination was shown to be detrimental to the formation of the monolayers. Determination of the valence band offsets in multifunctional oxide heterostructures provided a tool for insight in the electronic properties of these materials. The valence band offset for magnesium oxide grown epitaxially on silicon carbide was found to be 1.13±0.12 eV which is consistent with expected offsets based on the band gaps of the two materials. Future work will focus on determining repeatability and accuracy of the valence band offset measurements in various heterostructures.
Maximova, Natalia, "Application of the x-ray photoelectron spectroscopy for development of the niobium chemical mechanical process, photomodification of silicon for the field release mass spectrometer, and analysis of the multifunctional oxide heterostructures" (2008). Chemical Engineering Master's Theses. Paper 1. http://hdl.handle.net/2047/d10017975
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