Laser heating and annealing of hydrogenated amorphous silicon (a-Si:H) films is of interest for improved material properties. Due to the variety of possible laser treatments with regard to wavelength, pulse duration, scan time etc., the definition of laser impact on the material is a challenge which we try to approach by comparing properties of laser and oven treated materials. Here we report on the effect of oven heat treatment (up to TA= 575°C) on microstructure and hydrogen content of hydrogenated amorphous silicon films, as detected by measurements of infrared absorption and of effusion of hydrogen as well as of implanted helium. The latter technique has been found to measure isolated voids (cavities) of the size of silicon divacancies and larger. Undoped as well as phosphorus and boron doped plasma-deposited a-Si:H films of various hydrogen content (< 15 at.%) were investigated, including undoped device grade a-Si:H. The results show little indication for void-related microstructure in the as-deposited and annealed state for material with a concentration of silicon bonded hydrogen below 5 at. %. At higher hydrogen concentration, evidence is found that hydrogen out-diffusion due to annealing causes isolated voids in concentrations up to about 1020 cm-3. A possible mechanism for the annealing induced (micro-)void generation is discussed.

The problems of using performance parameters such as voltage, current and temperature measured with electrical sensors in today’s battery management systems (BMS) are well known. These parameters can be weakly informative about cell state, particularly as cells age, and contribute to over-conservative utilization and oversizing of a battery pack. Fiber optic (FO) sensors can offer an interesting alternative to conventional electrical sensors, with several advantages such as high selective sensitivity to various parameters, light weight, robustness to EMI, and multiplexing capabilities. In this study, a particular type of FO sensors, fiber Bragg grating (FBG) sensors were externally attached to lithium ion pouch cells for monitoring additional informative cell parameter such as strain and temperature. Multiple charge and discharge cycle were performed to examine the qualification of these signals for cell state estimation in BMS. In comparison to corresponding measurements using conventional electrical sensors, the FBG signals showed very promising results for utilization in effective BMS.

High-κ and metal gate structures have been used to improve the performance of CMOS devices. By changing the materials and structures of the gate dielectric stacks, the flatband voltage (VFB) and the leakage can be changed. We used bilayers and multilayer structures composed of MgO and Al2O3 to verify their influence on the overall electrical properties. Films with an MgO bottom layer generally are found with less flatband voltage shift and lower leakage than with an Al2O3 bottom layer. Also, the frequency dispersion and the interface state density (Dit) are higher for those with MgO bottom layers. MgO films thicker than 0.5 nm effectively shields the positive charges present in the Al2O3.

Mn-doped CeO2 electrolytes formulated as Ce1-xMnxO2-x (0.05 ≤ x ≤ 0.25) were prepared via soft chemical technique which involved co-precipitation of Mn2+ and Ce4+ using oxalic acid as the precipitant. The optimized pH for a stable incorporation of Mn dopant into ceria was found to be pH = 10. The solubility limit of MnO in the CeO2 fluorite lattice structure was suggested to be x = 0.20. The phase composition, morphology properties and elemental analysis of the oxalate and derived-powder was characterized using X-ray diffraction, SEM and X-ray fluorescence (XRF) respectively. The electrical conductivity of sintered samples of Mn-doped CeO2 ceramics were investigated in air using AC impedance spectroscopy. The bulk conductivities of the Mn-doped CeO2 ceramics sintered at 1200 °C at a test temperature of 800 °C were determined to be 4.223 x 10-4 ohm-1 cm-1 for Mn content x = 0.10 with activation energy, Ea = 0.88 eV.

The carbon-14 generated in Zircaloy (Zry) hull waste is considered an important radionuclide in the TRU waste geological disposal concept in Japan. Given that the metal Zry is highly corrosion-resistant in the anaerobic and low-temperature conditions of the repository, and that the C-14 release rate is assumed to be controlled by the corrosion rate, a variety of corrosion and leaching tests have been performed. However, since the Zry corrosion rate is extremely slow, it is not possible to predict long-term corrosion behavior through low-temperature corrosion tests conducted in a reasonable time period. A vast amount of testing has been conducted in the higher-temperature range of 523 to 633 K, and corrosion correlations have been obtained from these tests. Corrosion correlations have been used to predict the corrosion rate of Zry in a tuff repository. Long-term Zry autoclave corrosion data have been analyzed to develop new corrosion correlations. Extrapolating these correlations to a lower temperature range requires verification that the mechanisms do not change over the range of testing and extrapolation. Factors that influence corrosion rates under geological disposal conditions, such as material and environmental factors, should also be examined. Corrosion correlations, factors influencing corrosion rates, the results of corrosion and leaching tests, and a preliminary evaluation are discussed.

The front surface of dielectric passivated silicon wafers were spray coated with polyacrylic acid (PAA) using an ultrasonic coating system. A simple model was proposed to correlate the degree of coverage with the number of spray passes. The sprayed PAA films enabled good etching of the dielectric, using a process referred to as aerosol jet etching (AJE), despite the fact that the PAA thickness was non-uniform over the substrate. The AJE tip-to-substrate distance and diameter of the tip were tuned to balance process throughput and the etched line width. Controlling the level of condensation in the aerosol jet printer (AJP) fluid path was critical for etching 156-mm pseudo square silicon wafers.

We observed resistive switching in highly crystalline layered insulator hexagonal boron nitride (h-BN) under electric field in a nano-device configuration. Two distinct resistive states were observed in the 2D material heterostack. Electrical characterization using capacitance-voltage approach further revealed the role of h-BN as the active switching element. The switching behavior could be attributed to substitutional doping of h-BN under electric field present in the active region, possibly resulting in the formation of multi-element complex in which electrical conductivity depends on the amount of substituted dopant in the boron nitride crystal lattice. Since switching is observed independent of the direction of electric field, it is unipolar in nature. The observed memristance phenomenon in layered insulator may be potentially used in the form of NVM, providing possible direction to implement information storage or reconfigurable logic applications.

Here we report the first membrane-less biofuel cell made by using three-dimensional carbonaceous foam electrodes. We first developed a new synthetic pathway to produce a new carbonaceous foam electrode material with increased porosity both in the meso and macroporous scale. We proved that by increasing the porosity of our three-dimensional foams we could increase the current density of our modified electrodes. Then, by choosing the right combination of enzyme and mediator, and the right loading of active components, we achieved unprecedentedly high current densities for an anodic system. Finally, we combined the improved cathode and anode to build a new membrane-less hybrid enzymatic biofuel cell consisting of a mediated anode and a mediator-less cathode.

Rapid Thermal Oxidation (RTO) of AlGaN barrier has been employed to reduce the gate leakage current in AlGaN/GaN High Electron Mobility Transistors. Current Voltage (I – V) and Capacitance Voltage (C – V) characteristics of Schottky Barrier diodes and Metal Oxide Semiconductor diodes are compared. At room temperature, reduction in gate leakage current over an order of magnitude in reverse bias and four orders of magnitude in forward bias is achieved upon oxidation. While the gate current reduces upon RTO, gate capacitance does not change indicating gate control over the channel is not compromised. I – V and C – V characterization have been carried out at different temperatures to get more insight into the device operation.

The Knudsen Effusion Mass Spectrometer (KEMS) and the mechanistic MFPR (Module for Fission Product Release) code are tools which seem particularly interesting to support studies of the Instant Release Fraction (IRF) of Cs from spent nuclear fuel in a final repository. With KEMS, the thermal release of 137Cs and 136Xe were analysed by annealing up to total vaporization (2500K) of high burn-up (60 GWd/tU) Spent Nuclear Fuel (SNF) samples. Powder samples from the centre of the fuel, without high burn-up structure, were used. To determine the IRF, samples were analysed before and after being submitted to corrosion experiments in bicarbonated aqueous media.

MFPR was applied to determine the localization of Cs and fission gases in the SNF at the end of irradiation; the results are compared and supported by dedicated thermodynamics calculations performed for equilibrium conditions at various temperatures and fuel oxygen potentials by the non-ideal thermodynamic MEPHISTA (Multiphase Equilibria in Fuels via Standard Thermodynamic Analysis) database. A possible mechanism for Cs release during thermal annealing is proposed, taking into account inter-granular release and Cs oxide vaporization, atomic diffusion, ternary oxide phase formation and bubble release.

Differences in KEMS release profiles before and after submitting the samples to aqueous corrosion are attributed to the IRF and to changes in the vaporisation mechanism because of differences in the oxygen potential (pO2). The IRF of Cs estimated from the KEMS spectra, consisting on the part located at the grain boundaries and in inter-granular bubbles, is not significantly different from that corresponding to the experimental results found using classical static leaching experiments.

New experimental campaigns are being designed to confirm our interpretation proposed after this first run.

A porous composite formed of hollow graphene spheres with opens in them and amorphous carbon containing nitrogen and oxygenated groups has been fabricated by annealing the mixture of nanodiamond and polyacrylonitrile (PAN). Electrochemical tests on the electrode made of this material show that it may be a promising electrode material for supercapacitors. The relatively high capacitance is mainly attributed to the small inner electrical resistance, the huge specific surface area and the remaining nitrogen and oxygenated groups from the PAN.

In this work, sulfurizing metal precursors prepared by magnetron sputtering was applied in Cu2ZnSnS4 (CZTS) thin film fabrication. Three precursor structures, namely substrate/ Zn/(Cu&Sn), substrate/Zn/Cu/Sn/Cu and substrate/Zn/Sn/Cu, were compared for their synthesized CZTS film quality. It is notable that CZTS film made of the precursor structure of substrate/Zn/(Cu&Sn) has the best film quality with no obvious voids and biggest average grain size. When applying this precursor structure into device fabrication, a working CZTS device with an efficiency of 2.26% was made. The impact of metal precursors on the structural property of CZTS film were characterised by SEM, XRD, Raman and TEM. Thick MoS2 interfacial layer (∼200nm) between absorber and back Mo contact and ZnS formed in the front and back absorber regions are the possible reasons limiting short-circuit current and fill factor of the cell.

Ferromagnetic metal CoNi-based nano-objects have been synthesized in a polyol media within different elaboration conditions in order to drive their morphology (i.e. enhancing their length-to-diameter ratio ﴾d/L﴿, and changing the diameter d ratio over edge T width ﴾d/L﴿). Transmission Electron Microscopy (TEM) studies revealed unexpected effects on the Co80Ni20 nano-objects arising from the magnetic field assisted synthesis. This gave us the opportunity to compare this latter to coming from the variation of Ruthenium (III) chloride hydrate nucleating agent concentration. A Co80Ni20 anisotropic particles elaboration was successfully achieved under zero magnetic field assisted synthesis, while an important percentage of isotropic nanoparticles appeared immediately under the application of a small magnetic field (i.e. H > 500 Oe). In the first case we were able to sharply drive both the aspect ratio and head morphology of nanowires (T and ﴾d/T﴿). The good crystallinity and structures symmetry of all our samples have been proved by X-Ray Diffraction (XRD) pattern analysis. Magnetic static properties showed a ferromagnetic standard behavior with a coercive field efficiency which was strongly dependent on shape parameters. The magnetic static behavior was studied within a standard Stoner-Wohlfart model as a function of the observed morphologies. Our observations are fully consistent with a shape anisotropy origin behavior of the enhanced coercivity measured as function of the decreasing ﴾d/L﴿ ratio. However, they revealed the presence of contributions to the global effective anisotropy coming from other complex terms then the shape one (i.e. conic head impressiveness, dipolar interactions and magnetocrystalline anisotropy).

Organic solar cells, comprised of P3HT-fullerene blends, have the potential for photovoltaic energy applications. However, there is limited understanding of the mechanical behavior of these devices, and how this behavior can be tailored for optimal organic solar cell performance and device reliability. Therefore, a recently developed computational approach that is based on a constitutive representation of semi-crystalline polymers and fullerenes is used to identify the dominant morphological and microstructural characteristics that would affect the mechanical behavior of the active layer. The predictions indicate that stress and dislocation-density accumulation in interfacial regions and tie molecules play a significant role on the overall behavior.

Deep surface trap states present in hydrothermally grown ZnO nanorod (NR) arrays are monitored by photoelectrochemical and impedance spectroscopy. NR arrays were grown on a thin compact ZnO film deposited by pulsed laser deposition. Photocurrent responses upon square-wave illumination and lock-in detection of the as-grown NR arrays in the presence of Na2SO3 at pH 10 were characterized by a complex potential dependence indicating the presence of deep trap states. At a given frequency of light perturbation, the photocurrent amplitude increases as the potential bias is shifted towards values more positive than the flat band potential. Increasing the potential further than 0.8 V positive to the flat band potential leads to a decrease in the photocurrent amplitude. The potential of maximum photocurrent amplitude overlaps with a sharp decrease in the interfacial capacitance. The dependence of the photocurrent amplitude on bias potential strongly suggests the presence of deep electron trap states. The effect of the deep trap states are minimized by annealing of the NR arrays in air at 340° C.

In this paper we present a monolithically integrated wavelength selector based on a multilayer pi’n/pin a-SiC:H integrated optical filter that requires appropriate near-ultraviolet steady states optical switches to select the desired wavelengths in the VIS-NIR ranges.

Results show that the background intensity works as a selector in the infrared/visible regions, shifting the sensor sensitivity. Low intensities select the NIR range while high intensities select the visible part accordingly to its wavelength. Here, the optical gain is very high in the red range, decreases in the green range, and stays near one in the blue region decreasing strongly in the near-UV range. The transfer characteristics effects due to changes in steady state light intensity and wavelength backgrounds are presented. The relationship between the optical inputs and the output signal is established when a multiplexed signal is analyzed.

Ballistic grade composite materials have shown several advantages in comparison with their individual constituents, such as increased ballistic limit and reduced posterior trauma. One configuration in particular that has demonstrated greater ballistic efficiency is the arrangement of independent laminates (IL). It presents an increase in energy absorption compared to its counterpart of consolidated laminates (CL). In this study, an analysis is carried out to determine the effect on the ballistic performance of IL and CL arrangements when they are subjected to biaxial prestress (BP). Results show how the ballistic advantage obtained in IL is nullified in comparison with CL, thus demonstrating the limitations of this arrangement for possible applications where the arrangement is subjected to normal impacts with BP.

Despite being well versed in scientific and technical concepts, engineering students often struggle with technical writing and communication. The CLEAR (Communication, Leadership, Ethics and Research) program at the University of Utah prepares engineering undergraduates for success in their careers through coursework aimed to improve oral and written communication skills, teamwork and ethical understanding. Along with an evaluation of ongoing CLEAR curricula in engineering laboratory and design classes, we are developing tools to assess student outcomes as defined by ABET criteria. These outcomes will inform how best to implement CLEAR curricula at the University of Utah, and ensure our graduates are better prepared to join the engineering workforce.

Currently, organic photovoltaics are not a viable renewable source of energy in comparison to silicon solar panels because of its low efficiencies, due to its disorganized morphology which leads to charge recombination and an overall loss of energy production. It was hypothesized that simultaneously organizing the morphology and increasing the area of the active sites for exciton dissociation would improve overall efficiency.

Our synthesized gold-graphene (AuRGO) was dispersed in sulfonated polystyrene (PSS) and added to the active layer. We also blended polymethylmethacrylate (PMMA) with graphene, which was then incorporated into the active layer. AFM imaging demonstrated that the polymers self-assembled into column structures. Additionally, the AuRGO showed an affinity for both P3HT and the PSS, migrating to the interfaces. Solar simulation results show that both polymer-graphene blends demonstrated enhanced current and efficiency.

The self-organization helped increase the efficiency of both samples, but the AuRGO/PSS had a greater efficiency improvement over the cG/PMMA by 170%. This increase is attributed to the fact that since the AuRGO migrated to the interfaces, the sheet acts as a bridge that improved the electron flow through a connection between the electron donating and accepting materials, improving exciton dissociation and charge transport, and therefore efficiency.

The phase composition and the microstructure of multilayer ceramics synthesized by directed laser treatment of ternary powder mixtures of Al2O3–TiO2–Y2O3 have been studied. It is established that at R = 2.34 (where R is TiO2/Y2O3 in mol %) the main phases observed are Y2Ti2O7, α-Al2O3 and a little amount of β-Al2TiO5. The content of the formed phases is determined by the composition of the initial mixtures. The texture of the surface and the microstructure of the formed ceramics depend on the α-Al2O3 and Y2Ti2O7 content. Increasing the content of alumina in the initial mixtures, the surface of the ceramics is saturated by α-Al2O3 crystallites. When a multi-layer synthesis is realized, the Y2Ti2O7 phase is concentrated at the boundary between the two adjacent layers (top and bottom). In the underlying layer, the growth of the corundum crystallites is prolonged due to the additional heating.