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Product miniaturization is an ever increasing customer demand in aerospace, bio-medical, defense and electronics industries. These microparts play a vital role and are required to abide by stringent norms set forth by various quality control agencies. To maintain their functionality over a period of time, they are made of special engineering materials rather than silicon as commonly used in microelectronics. Lithography, etching, embossing, electroplating, laser machining and other micro manufacturing techniques have been employed traditionally to manufacture microcomponents; however, these techniques would be expensive, cause surface damage, or produce a very rough surface. Electrochemical polishing is capable of machining/polishing any conducting material while holding close dimensional tolerances. This research develops a high frequency electrochemical nanopolishing technique for commercially pure alpha titanium. An alcohol and salt based electrolyte was used with direct current as well as alternating current on alpha titanium plate. For both current types, optimal surface roughness R_(a) ~ 300 nm was obtained on poly grained surface using interferometry and ~ 2 nm within a single grain by atomic force microscopy. Comparable results were obtained by other researchers with 30-120 nm R_(a) for titanium and titanium alloys. Linear regression models were developed to predict the surface roughness. The surface roughness predicted by the models was found to be within 26% of the measured values.

Polymer light emitting electrochemical cells (LECs) are solid-state devices containing an active layer blend of luminescent polymer, ion transport material and salt sandwiched between two electrodes. They operate on the principal of in situ electrochemical doping. Doping entails the injection of electronic charge from the electrodes, causing the reduction/oxidization of the luminescent polymer, and accompanied by charge compensation through the redistribution of salt counter-ions. Due to the high conductivity of the doped polymer, a fully turned on LEC has a dramatically reduced contact and bulk resistance. This gives the LEC certain intrinsic advantages such as balanced charge injection, low operating voltage and high quantum efficiencies, even when stable metal or symmetric electrodes are used. These properties have led to the popular assumption that the electrode work function is not a critical device parameter for LEC operation. In this thesis, I describe my original research to determine how the electrode composition influences LEC performance. A series of sandwich and planar configuration LECs with various electrodes on identical MEH-PPV (poly[5-(2-ethylhexyloxy)-2-methoxy-1,4-phenylene vinylene]):PEO (poly ethylene oxide):LiTr (Lithium trifluoromethanesulfonate) based films are constructed. I demonstrate that the doping profile, doping propagation speed, emission zone shape, emission zone location, electro-luminescence (EL) turn-on, and EL efficiency are all strongly affected by the choice of electrode materials. LECs with asymmetrical electrodes optimized for both electron and hole injection result in the best overall performance. Using an optimized electrode configuration, I am able to realize extremely large crown ether based planar LECs. MEH-PPV: dicyclohexano-18-crown-6 (DCH18Cr6): LiTr and 108GE:DCH18Cr6:LiTr devices with various symmetric and asymmetric electrode configurations were constructed, where 108GE is the fluorene copolymer poly[(9,9-dioctyl-2,7-divinylene-fluorenylene)-alt-co-(2-methoxy-5-(ethylhexyloxy)-1,4-phenylene)]. I demonstrate ii i and image the first ever crown ether-based planar LECs with millimeter inter-electrode spacing. Due to minimal phase separation, crown ether-based LECs display highly uniform doping propagation and very smooth emission zones. Junction relaxation, de-doping and reverse bias operation experiments are also presented, and results compared to behavior in PEO based LECs. Additionally, I demonstrate that crown ether-based LECs do not exhibit frozen junction behavior at room temperature. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2008-09-23 16:15:06.569

Light-emitting electrochemical cells (LECs) are solid state polymer devices operating through the formation of a light-emitting p-n junction by in situ electrochemical doping. The LEC film contains a luminescent polymer and a polymer electrolyte. A sufficiently high voltage bias initiates the electrochemical p-doping reaction at the anode interface and n-doping reaction at the cathode interface. With time the doped regions expand in volume until they make contact to form a light-emitting p-n junction. In this thesis, I present my original research on both the light-emitting and photovoltaic properties of LECs. I discovered that continued doping after p- and n-doped regions have made first contact accounts for most of LEC turn-on time. I showed that because the electronic charges must be injected from an external circuit for the electrochemical doping to occur, the LEC turn-on response is limited to no faster than milliseconds. I also demonstrated that the lifetime of LECs can be affected by various factors such as stress temperature, stress current, substrate thermal conductivity, and luminescent polymer end group. With the right combination of substrates and materials, LECs exhibit a remarkable half lifetime on the order of hundreds of hours when stressed at a current density of 1A/cm2. I also observed that an as-formed p-n junction can even relax into a p-i-n junction upon the removal of applied voltage bias. A p-i-n junction LEC exhibits more efficient electroluminescence due to less photoluminescence quenching in the quasi-intrinsic emission zone. Frozen p-i-n junction LECs also exhibit a much improved photovoltaic response. By carefully controlling the relaxation (dedoping) temperature and duration, I have demonstrated p-i-n junction photovoltaic cells with record-high open-circuit voltage of 2.25V and short-circuit current density in excess of 10mA/cm2 under simulated sunlight of ~300mW/cm2. By optimizing film thickness and electrolyte content, I have achieved a thirty-fold increase in power conversion efficiency of p-i-n junction photovoltaic cells. My results demonstrate that a polymer homojunction such a p-n or a p-i-n junction is a promising device concept that has potential application in high performance polymer-based photonic devices. / Thesis (Ph.D, Physics, Engineering Physics and Astronomy) -- Queen's University, 2009-05-25 13:06:45.646

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This thesis is concerned with the development and laboratory assessment of an electrochemical sensor for the detection and measurement of the volatile inhalation anaesthetic, forane. Investigations were therefore based on the heterogeneous and homogeneous reduction of this agent in non-aqueous electrolyte. Preliminary experiments at a mercury and other rotating disc electrodes (RDEs) revealed that the direct reduction of forane was not possible and therefore the use of an electron transfer mediator was examined. To this end, the radical anion of the polyaromatic compound, fluoranthene, (F), was investigated as a possible electro-reduction catalyst and the mediated reduction of the anaesthetic, via a catalytic process, demonstrated. Theory was presented for the calculation of chronoamperometric and steady state responses at the RDE resulting from one electron transfer and coupled (catalytic) homogeneous kinetic processes. The latter enabled a precise mechanism to be assigned to the F + forane process, while a comparison of the former theory with experimental chronoamperometric results was used, in conjunction with AC impedance studies, to investigate the adsorption of F at the mercury/acetonitrile interface. A polymer modified electrode, based on the polymer poly-(11-vinylfluoranthene) was demonstrated to be effective in the heterogeneous reduction of forane but displayed only a limited lifetime. Therefore, a Clark-type membrane electrode was constructed and the detection and measurement of forane, in the absence of oxygen, demonstrated using this device. However, the sluggish response of this sensor, together with interference problems from oxygen encouraged the development of a device which utilised a channel electrode (ChE) sensing approach. Theory was presented for the deduction of steady state currents at the ChE resulting from coupled catalytic kinetics and this was used to demonstrate that the same mechanism for the F + forane system operated at the ChE as the RDE. The conventional ChE was then modified by the incorporation of a membrane and this sensor, which was shown to operate successfully in the presence of high concentrations of oxygen and nitrous oxide, responded linearly to forane, while displaying an excellent response time of under ten seconds. The device should find application in clinical monitoring.

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