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.

Multifunctional Pr3+-doped GdPO4 nanocrystals possessing UV, visible emissions and magnetic properties were synthesized via co-precipitation and following annealing. It was revealed that as-prepared GdPO4 nanorods were transformed to nanoparticles after heat treatment at 900 °C for 2 hours. Ultimately, GdPO4:Pr3+ nanoparticles have strong UV emission under the excitation of 275 nm and visible emission under the excitation of 445 nm, which offers the optical modalities in both UV and visible range. Moreover, Gd3+-containing nanoparticles are efficient T 2 -weighted (negative) magnetic resonance (MR) contrast agents due to the presence of Gd3+ ions, which can be potentially applied as multimodal, photoluminescence-magnetic resonance imaging contrast agent.

With increasing density imposed by external osmotic pressure, DNA in univalent salt solutions (e.g., NaCl) is known to go through a set of ordered mesophases, eventually crystallizing into an orthorhombic crystal. While the transition from the cholesteric to the line hexatic (LH) phase has been observed before, it has remained unclear whether the transition is of second order or first order. We use the small but accurately measurable temperature dependence of the osmotic pressure of a PEG solution to fine-regulate the osmotic stress with which it acts on the DNA subphase. This allows us to set the osmotic pressure to an accuracy never achieved before. This advance in experimental methodology allows us then to detect small but nevertheless finite changes in the density of DNA as it goes through the cholesteric → LH transition. In this way, we first determine experimentally the small density change that occurs at the cholesteric → LH phase transition. Further, we establish that this small density discontinuity of Na-DNA is merely increased when polyvalent salt Co(NH3)6Cl3, i.e. CoHex, is added to the solution. Increasing CoHex concentration finally leads to a phase separation at zero imposed osmotic pressure. Establishing a continuity of thermodynamic states for the cholesteric → LH transition and DNA condensation, thought to be completely unrelated before, represents an important advance in our understanding of DNA polymorphism in electrolyte solutions.

The silicon carbide (SiC) market is gaining momentum hence productivity in device manufacturing has to be improved. The current transition from 100 mm SiC-wafers to 150 mm SiC-wafers requires novel processes in the front-end as well as the back-end of SiC-chip production. Dicing of fully processed SiC-wafers is becoming a bottleneck process since current state-of-the-art mechanical blade dicing faces heavy tool wear and achieves low throughput due to low feed rates in the range of only a few mm/s. This paper presents latest results of the novel dicing technology Thermal Laser Separation (TLS) applied for separating SiC-JFETs. We demonstrate for the first time that TLS is capable of dicing fully processed 4H-SiC wafers, including back side metal layer stacks, process control monitoring (PCM), and metal structures inside the dicing streets with feed rates up to 200 mm/s. TLS thus paves the way to efficient dicing of 150 mm SiC-wafers.

Topological insulators are a new class of materials with the ability to carry spin-polarized currents on their surfaces. Nuclear magnetic resonance (NMR) measurements can probe the magnetic interactions between specific isotopes and the electronic system of a material. We present 209Bi NMR spectra and relaxation rate data on single crystals of the topological insulator material Bi2Se3 grown under various conditions. Our NMR data on single crystals reveal a significant strength of coupling between the nuclear spins and the bulk carrier spins, suggesting that nuclear spins may have a sizeable effect on spin-polarized surface currents.

Self-powered microsystems as an alternative to standard systems powered by electrochemical batteries are taking a growing interest. In this work, we propose a different method to store the energy harvested from the ambient which is performed in the mechanical domain. Our mechanical storage concept is based on a spring which is loaded by the force associated to the energy source to be harvested [1]. The approach is based on pressing an array of fine wires (fws) grown vertically on a substrate surface. For the fine wires based battery, we have chosen ZnO fine wires due the fact that they could be grown using a simple and cheap process named hydrothermal method [2]. We have reported previous experiments changing temperature and initial pH of the solution in order to determine the best growth [3]. From new experiments done varying the compounds concentration the best results of fine wires were obtained. To characterize these fine wires we have considered that the maximum load we can apply to the system is limited by the linear buckling of the fine wires. From the best results we obtained a critical strain of εc = 3.72 % and a strain energy density of U = 11.26 MJ/m3, for a pinned-fixed configuration [4].

Imaginary contact angles underlying hyperhydrophilicity and the Inverse Lotus Effect introduce a fundamental new development in the area of contact angles and wettability. Just as the Lotus Effect expanded hydrophobicity beyond the maximal contact angle of 119° on a smooth surface, the Inverse Lotus Effect expands hydrophilicity beyond the minimal contact angle of 0° on a smooth surface. Imaginary dynamic contact angles thus offer an exciting enhancement in tools and methodology for measuring the wettability on rough, highly hydrophilic surfaces. Contrary to current thinking, full or perfect wetting of rough surfaces is only little understood and cannot be predicted by classical equations. Therefore also the exact physical basis of imaginary dynamic contact angles remains to be elucidated. In this short treatise some aspects of the new field will be treated with examples derived from rough titanium surfaces employed in the medical field.