My dissertation focuses on (i) the development sputtered films for solid phase microextraction (SPME) and (ii) the comprehensive characterization of materials using a suite of analytical techniques. Chapter 1 reviews the basics of SPME. This chapter also contains (i) a discussion of various sputtering techniques, (ii) a discussion of two techniques I focused on most of my work: spectroscopic ellipsometry (SE) and X-ray photoelectron spectroscopy (XPS). Chapter 2 focuses the major part of my work, which is to prepare new solid phases/adsorbents for SPME via silicon sputtering followed by thermal deposition of a polymer, polydimethylsiloxane (PDMS). PDMS was deposited by a simple gas phase technique which has never before been applied to prepare SPME stationary phases. The coatings were characterized by time-of-flight mass spectrometry (ToF-SIMS), XPS, scanning electron microscopy (SEM), SE, and contact angle goniometry. The extraction efficiencies of ca. 1.8 µm sputtered, PDMS-coated fibers were compared to a commercial fiber (7 µm PDMS) for a series of polycyclic hydrocarbons (PAHs). Large carry-over and phase bleed peaks are observed in case of commercial PDMS-based SPME coatings, which decrease the lifetime and usefulness of these fibers. It is of great significance that our sputtered fibers exhibit very small or negligible carry-over peaks and phase bleed peaks under the same conditions. Chapter 3 focuses on the multi-instrument characterization of copper and tungsten films sputtered by direct current magnetron sputtering (DCMS) and high-power impulse magnetron sputtering (HiPIMS) using a modern sputter source. The resulting films were characterized by energy dispersive X-ray spectroscopy (EDX), XPS, SEM, atomic force microscopy (AFM), SE, and X-ray diffraction (XRD). By EDX and XPS, all the sputtered films only showed the expected metal peaks. By XPS, the surfaces sputtered by DCMS were richer in oxygen than those produced by HiPIMS. By AFM, both surfaces were quite smooth. By SEM, the HiPIMS films exhibited smaller grain sizes, which was further confirmed by XRD. The crystallite sizes estimated by XRD are as follows: 18.2 nm (W, HiPIMS), 27.3 nm (W, DCMS), 40.2 nm (Cu, HiPIMS), and 58.9 nm (Cu, DCMS). By SE, the HiPIMS surfaces showed higher refractive indices, which suggested that they were denser and less oxidized than the DCMS surfaces. Chapter 4 reports characterization of liquid PDMS via SE, which required some experimental adaptations. The transmission measurements were obtained via a dual cuvette approach that eliminated the effects of the cuvettes and their interfaces. Only the reflection measurements were modeled with a Sellmeier function which produced decent fits. Chapters 5 consists of contributions to Surface Science Spectra (SSS) of near-ambient XPS spectra of various unconventional materials including cheese, kidney stone, sesame seeds, clamshell, and calcite. This dissertation also contains appendices of tutorial articles I wrote on ellipsometry and vacuum equipment.
| Identifer | oai:union.ndltd.org:BGMYU2/oai:scholarsarchive.byu.edu:etd-10285 |
| Date | 10 October 2019 |
| Creators | Roychowdhury, Tuhin |
| Publisher | BYU ScholarsArchive |
| Source Sets | Brigham Young University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
| Rights | https://lib.byu.edu/about/copyright/ |
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