Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 116-126).

Thesis (Ph. D.)--State University of New York at Binghamton, Department of Materials Science, 2006. / Includes bibliographical references.

<p>Tantalum diffusion barrier coatings were investigated as a way to improve the conversion efficiency of CIGS (copper indium gallium diselenide) solar cells.  Tantalum coatings were deposited upon silicon and stainless steel foil substrates using direct current magnetron sputtering (DcMS) and high power impulse magnetron sputtering (HiPIMS).  The coatings were characterized using scanning electron microscopy (SEM).  Cross-sectional scanning electron micrographs revealed that the HiPIMS coatings appeared denser than the DcMS coatings.</p>

No description available.

The long-term goal of this research project is the development of solution-based inorganic dielectric and semiconductor materials for inkjet printed electronics. The main focus of this thesis involves testing of the materials and devices under development. A new solution-based inorganic dielectric material (HfOSO₄), given the name hafsox, is developed and shows excellent dielectric properties. Hafsox with the addition of lanthanum, to improve film dehydration, has successfully been demonstrated as a gate dielectric. Metal-insulator-metal (MIM) capacitance testing of hafsox with lanthanum, has resulted in a low loss tangent of 0.30% at 1 kHz, a relative permittivity of 11.47 at 1 kHz, a breakdown voltage of 6.30 MV cm⁻¹, and a leakage current density of 4.38 nA cm⁻² at 1 MV cm⁻¹. Progress has also been achieved in the development of solution-based semiconductor materials. To date the most successful of these materials is zinc indium oxide (ZIO), which has been demonstrated as a thin-film-transistor (TFT) channel material. This ZIO TFT is a depletion-mode device with a turn-on-voltage of V[subscript on]~ -19 V, a threshold voltage of V[subscript T] ~-16 V, and a drain current on-to-off ratio of ~10³. Mobilities extracted from this ZIO TFT include an incremental mobility of μ[subscript inc] ~0.05 cm² V⁻' sec⁻', an effective mobility of μ[subscript eff] ~0.02 cm² V⁻' sec⁻', and an average mobility of μ[subscript avg] ~0.02 cm² V⁻' sec⁻' at V[subscript GS]=20 V. The development of metal-semiconductor field-effect transistors (MESFET) TFTs is also investigated as a means of eliminating the need for a dielectric material in order to reduce the complexity of fabricating circuits. MESFETs are attempted with semiconductor materials such as CdS that is deposited by chemical bath deposition (CBD) and SnO₂ that is deposited by RF magnetron sputtering, but with little success. The most successful MESFET-like device fabricated, employing SnO₂ as the channel material, is a strong depletion-mode device with a small amount of gate voltage modulation. / Graduation date: 2006

Graduation date: 1998

Solid state thin film lithium microbatteries fabricated by pulsed-laser deposition (PLD) are suggested. During deposition the following process parameters must be considered, which are laser energy and fluence, laser pulse duration, laser pulse frequency, target composition, background gasses, substrate temperature, target-substrate distance and orientation. The effects of the variations of the process parameters can be obtained by measuring stoichiometry, thickness, phases and structure (grain size and texture), and stress of the deposited films. Electrochemical measurements will be conducted to test the microbattery properties through open-circuit voltage, charge-discharge cycling, cyclic voltammetry, and impedance analysis. / Singapore-MIT Alliance (SMA)

TiNi films were prepared by co-sputtering TiNi target and a separate Ti target. Crystalline structure and phase transformation behaviors of TiNi films were investigated. Results showed that TiNi films had fine grain size of about 500 nm and fully martensitic structure at room temperature. X-ray photoelectron spectroscopy (XPS) results indicated that there is adherent and natural TiO₂ film, which is beneficial to its corrosion resistance and biocompatibillity. Results from differential scanning calorimeter (DSC), in-situ X-ray diffraction (XRD) and curvature measurement revealed clearly martensitic transformation upon heating and cooling. The TiNi films were further deposited on micromachined silicon cantilever and membrane structures in order to form micro-gripper or microvalve with large deformation due to shape-memory effect. / Singapore-MIT Alliance (SMA)

We have investigated a series of molecular and polymeric approaches for generating adherent thin films that impart anti-fouling characteristics to oxide surfaces. These films incorporate oligo- or poly(ethylene glycol) moieties that are expressed in high density in the near-surface region. In our molecular approach, oligo(ethylene glycol)-terminated n-alkyl-trichlorosilanes, RO(CH₂CH₂O)₃(CH₂)₁₁SiCl₃, have been designed so to spontaneously adsorb onto oxide surfaces and produce densely packed films. Another strategy uses a surface initiated polymerization to generate reactive anchored polymer chains that are then chemically modified to incorporate oligo(ethylene glycol) units. Lastly, a comb copolymer comprising a poly(acrylic acid) backbone and different grafting ratios of a linear poly(ethylene oxide-r-propylene oxide) chain has been prepared that adsorbs onto surfaces and forms a poly(ethylene glycol)-exposing film in single step. These surface coatings provide varying levels of protein and cellular resistance that can be related to molecular-scale elements of their surface structure. / Singapore-MIT Alliance (SMA)

In this paper, some critical issues and problems in the development of TiNi thin films were discussed, including preparation and characterization considerations, residual stress and adhesion, frequency improvement, fatigue and stability, as well as functionally graded or composite thin film design. Different types of MEMS applications were reviewed and the prospects for future advances in fabrication process and device development were discussed. / Singapore-MIT Alliance (SMA)