We report a large enhancement of thermally injected spin current in normal metal (NM)/antiferromagnet (AF)/yttrium iron garnet (YIG), where a thin AF insulating layer of NiO or CoO can enhance the spin current from YIG to a NM by up to a factor of 10. The spin current enhancement in NM/AF/YIG, with a pronounced maximum near the Neel temperature of the thin AF layer, has been found to scale linearly with the spin-mixing conductance at the NM/YIG interface for NM = 3d, 4d, and 5d metals. Calculations of spin current enhancement and spin mixing conductance are qualitatively consistent with the experimental results.

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Polymer Light-Emitting Electrochemical Cells (PLECs) are solid state devices based on the in situ electrochemical doping of the luminescent polymer and the formation of a p-n junction where light is emitted upon the application of a bias current or voltage. PLECs answer the drawbacks of polymer light-emitting diodes as they do not require an ultra-thin active layer nor are they reliant on low work function cathode materials that are air unstable. However, because of the dynamic nature of the doping, they suffer from slow response times and poor stability over time. Frozen-junction PLECs offer a solution to these drawbacks, yet they are impractical due to their sub-ambient operation temperature requirement. Our work presented henceforth aims to achieve room temperature frozen-junction PLECS. In order to do that we removed the ion solvating/transporting polymer from the active layer, resulting in a luminescent polymer combined solely with a salt sandwiched between an ITO electrode and an aluminum electrode. The resulting device was not expected to operate like a PLEC due to the absence of an ion-solvating and ion-transporting medium. However, we discovered that the polymer/salt devices could be activated by applying a large voltage bias, resulting in much higher current and luminance. More important, the activated state is quasi static. Devices based on the well-known orange-emitting polymer MEH-PPV displayed a luminance storage half-life of 150 hours when activated by forward bias (ITO biased positively with respect to the aluminum) and 200 hours when activated by reverse bias. More remarkable yet, devices based on a green co-polymer displayed no notable decay in current density or luminance even after being stored for 1200 hours at room temperature! PL imaging under UV excitation demonstrates the presence of doping. These devices are described herein along with an explanation of their operating mechanisms. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2013-11-29 17:40:19.152

Transparent InO (Indium oxide) thin-film transistors fabricated by reactive ratio frequency (rf) magnetron sputtering at room temperature were demonstrated on glass and plastic substrates. The resistivity, transmittance, X-ray diffraction pattern, and surface morphology of the films prepared at a 50% oxygen partial pressure were investigated, the resistivity and the average transmittance of the films were 4.2¡Ñ104 £[-cm and 87 %, respectively. In addition, Indium tin oxide (ITO) and silicon nitride (SiNX) thin films were used as the electrode and gate insulator. The resistivity and the average transmittance of ITO electrodes were 7¡Ñ10-4 £[-cm and 85%. On the other hand, the maximum leakage current of less than 10-9A/cm2 was obtained for the SiNX layer at an electric field of 1 MV/cm. For the InO TFT on glass substrate with 6 £gm channel length and 20 £gm channel width, the measured saturation mobility, threshold voltage, on/off ratio and subthreshold swing are 9.39V-1s-1, 1.5V, 2.2¡Ñ107and 0.5 V/decade. For the TFTs prepared on plastic substrate, the measured saturation mobility, threshold voltage, on/off ratio and subthreshold swing are 8.19V-1s-1, 1.83V, 1.43.¡Ñ106and 0.8 V/decade, respectively.

The existence of Room Temperature Ionic Liquids (RTILs) has been known for a long time, but only recently have they been pulled to the forefront of chemical research. This increase in attention can be attributed to a keen interest in their intrinsic properties for a wide variety of potential applications. RTILs have been used as alternative solvents for organic synthesis as well as catalysis, as well as supports for the purification or extraction of metals. Being ionic in nature and liquid at temperatures below 100°C, RTILs lend themselves to the electrochemist. As a result, they have been looked at for use in electrochemical systems such as high capacity batteries and supercapacitors. Due to their extremely high density of charge carriers relative to more well-known aqueous electrochemical systems, a new theoretical approach must be taken. Currently, a large gap exists between theoretical approaches and experimental results. The work contained within this thesis aims to provide insight into the interface between a RTIL and an electrified gold electrode.

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Cerium oxide (ceria, CeOâ‚‚) is a rare earth oxide that has attracted wide-spread research interest because of its unique properties such as high mechanical strength, oxygen ion conductivity, oxygen storage capacity and autocatalytic property. In recent years, researchers have discovered that ceria nanoparticles (NPs) are capable of protecting cells from free radical induced damage. Interestingly, it was found that nanometer size (~ 5 nm) ceria can scavenge free radicals quite efficiently, thus acting as an anti-oxidant. This phenomenon has been explained based on the autocatalytic property of ceria NPs. Several methods have been developed for the synthesis of ceria NPs that include flame combustion, hydroxide co-precipitation, hydrothermal/solvothermal, microemulsion, sonochemical and microwave-assisted heating methods and sol-gel method. Ceria NPs synthesized by these methods are often highly aggregated. Furthermore, large scale synthesis of monodispersed CeOâ‚‚ NPs is quite challenging. Therefore it is desirable to synthesize ceria NPs in bulk quantity keeping its important properties intact, specifically free-radical scavenging property. The main goal of this study is therefore to synthesize ultra-small ([less than]5.0 nm), high quality monodispersed ceria NPs in large quantities. In this thesis work, I present a couple of room temperature techniques, dilute sodium hydroxide (NaOH) assisted and ethylenediamine (EN) assisted for the synthesis of nearly mono-dispersed, ultra-small ( < 5 nm) and water-dispersible ceria NPs. Morphology and particle size of the ceria NPs were investigated through high resolution transmission electron microscopy (HRTEM). The HRTEM analysis confirmed the formation of 3.0 ± 0.5 nm size and 2.5 ± 0.2 nm size highlycrystalline ceria NPs when synthesized using dilute NaOH and EN as solvents, respectively. The nanostructures were characterized by X-ray diffraction (XRD) studies to determine the crystal structure and phase purity of the products. The samples were also thoroughly characterized by X-ray photoelectron spectroscopy (XPS) to determine the oxidation state of cerium ions. The presence of the +3 and +4 oxidation states in the samples was also confirmed from the XPS analysis. The co-existence of these two oxidation states is necessary for their applications as free radical scavenger. The autocatalytic behaviors of the ceria NPs were investigated through a hydrogen peroxide test and monitored by UV-visible transmission spectroscopy.

High entropy alloys (HEAs) based on refractory elements have shown a great potential for high temperature structural applications. In particular, the ones containing Al, exhibits a microstructure similar to the γ-γ' in Ni-based superalloys. While these alloys exhibit impressive strengths at room temperature (RT) and at elevated temperatures, the continuous B2 matrix in these alloys is likely to be responsible for their brittle behavior at RT. Phase stability of five such alloys are studied by thermo-mechanical treatments and characterization techniques using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Two of these alloys showed an inverted microstructure, where the disordered BCC phase becomes continuous, and therefore, they were characterized in detail using SEM, TEM, atom probe tomography (APT) and synchrotron x-ray diffraction experiments. The phenomenon of phase inversion lead to a better combination of strength and ductility as compared to the non-inverted microstructure.To enhance the stability of B2 intermetallic phase which provides the strength when present in a BCC matrix, multicomponent B2 phase compositions stable at 1000°C in some of the above studied alloys, were melted separately. The aim was to establish a single phase B2 at 1000°C and understand the mechanical behavior of these single-phase multicomponent B2 intermetallic alloys. These alloys exhibited a ductile behavior under compression and retained ~1 GPa yield strength at temperature up to 600°C. The ductile nature of these alloys is attributed to the change in bonding nature form directional to metallic bonding, possibly resulting from a significantly high configurational entropy compared to binary or ternary stoichiometric B2 compounds.

A discovery of the neutron's permanent electric dipole moment larger than the standard model prediction of dn ≈ 10-31 e·cm would signal a new source of CP-violation and help explain the matter-antimatter asymmetry in the universe. Tightening the limits on dn constrain extensions to the standard model in a complementary fashion to the atomic and electron EDM searches. The recent upgrade of the Los Alamos ultracold neutron source makes it possible for a new room temperature search with the statistical reach to improve upon current limits by a factor of 10 or more. During the 2018 LANSCE cycle a prototype apparatus was used to demonstrate the capability to transport and manipulate polarized neutrons and perform Ramsey and Rabi sequence measurements. I will report on the measurements made over the last year, efforts underway to upgrade the prototype chamber, and possible future upgrades of the ultracold neutron source.