Preferentially {100} oriented and polycrystalline platinum electrodes were prepared by potentiostatic electrodeposition. The surface of the electrodes was characterized by deconvolution of the hydrogen desorption region. The catalytic activity for formic acid oxidation was determined by cyclic voltammetry and chronoamperometry. The results indicate that although the maximum current observed in cyclic voltammogram does not increase, the long term performances as measured by chronoamperometry dramatically increase up to 33 times with increased Bi coverage despite the loss of electroactive Pt surface area.

In this work, the metallic element Ru is introduced into a-Si:H. The structural and electrical properties of the films doped with Ru have been investigated. Raman spectra reveal that the addition of Ru disarranges further the intrinsically disordered amorphous network and generates more coordinated defects. Meanwhile, a new paramagnetic signal, associated with the holes localized in valence band tail, has been observed. Moreover, the conductivity increases by about nine orders of magnitude with the increase of doping concentration, and the temperature coefficient of resistance (TCR) results show that this material may have a potential application in the infrared detectors.

Papers in the Appendix were published in electronic format as Volume 1534

We present a systematic study of photo- and cathodoluminescence measurements in the visible of Terbium doped SiC:H and AlN thin films. The Terbium atomic concentrations vary from 0.9 to 10% for the SiC:H and from 0.8 to 6% for the AlN samples. For both materials the increase of the emission intensity with concentration and the subsequent quenching effect can be seen. The optimal concentration for the highest light emission is found. Photoluminescence excitation spectroscopy addresses the enhancement light emission mechanisms of the principal emission electronic transition of Terbium at ∼542 nm.

The thermopower properties of GaN nanowires with transitional metal impurities are investigated in the framework of constrained spin density functional theory (DFT) calculations. The nanowires are connected to nanoscopic Al[111] electrodes, which ensure a natural coupling to the wurtzite structure of the nanowires. We investigate the thermoelectric properties comparatively for the pristine GaN nanowire and the system with one Mn adatom. Our study points out the predicted qualitative behavior for systems with a peak in the total transmission, as well as the sign change in the thermopower. For the system with the magnetic impurity we find an enhanced conductance, thermopower and figure of merit. The detectable spin current polarization suggests the device structure may be also used in low temperature sensing applications.

Metal ferrite nanoparticles are of considerable technological and theoretical interest. Magnetic response of these systems is a function of various system properties like saturation magnetization, growth orientation, average particle size and size distribution, volume concentration, etc. [1]. This preliminary study investigates the magnetization dynamics (and thereby the Verdet constant) of aqueous Fe3O4 nanoparticle solutions through precision AC measurements of the Faraday Rotation (FR) at 633 nm for three different Fe3O4 nanoparticle solutions that are all prepared to have the same average particle size (∼10 nm) but differing saturation magnetization values. For each of these nanoparticle solutions precision measurements for FR are carried out over a given range of volume concentrations. The study shows simple linear dependence of FR on volume concentration and a more involved dependence on saturation magnetization. Some preliminary results relating to the frequency dependence of Verdet constants are also presented. Future directions for this work are also discussed. It is hoped that that these results will help in the development of better models to characterize response of these technologically and fundamentally useful systems.

Gallium nitride (GaN) nanowires exist in a myriad of cross-sectional shapes. In this study, a series of classical molecular dynamics simulations is performed to investigate the strain-phononics-structure relationship in rectangular and triangular wurtzite (Wz) - GaN nanowires. The thermal conductivity of the nanowires is linearly dependent on the uniaxial strain in both compressive and tensile regimes, and shows no significant dissimilitude for the same amount of strain exerted on the two types of nanowire. This is coherent with an analytical approach using the Boltzmann transport theory. However, the thermomechanical behaviour at the vertex regions shows palpable differences between the two subfamilies, relative to the non-vertex faceted regions, as the structural morphology is most disparate at the vertices.

Metal-insulator-metal (MIM) capacitors for DRAM applications have been realized using TiO2/ZrO2/TiO2 (TZT) and AlO-doped TZT (TZAZT and TZAZAZT) dielectric stacks. High capacitance densities of about 46.6 fF/μm2 (for TZT stacks), 46.2 fF/μm2 (for TZAZT stacks), and 46.8 fF/μm2 (for TZAZAZT stacks) have been achieved. Low leakage current densities of about 4.9×10−8 A/cm2, 5.5×10−9 A/cm2, and 9.7×10−9 A/cm2 (at -1 V) have been obtained for TZT, TZAZT, and TZAZAZT stacks, respectively. We analyze the leakage current mechanisms at different electric field regimes, and compute the barrier heights. The effects of constant current stress and constant voltage stress on the device characteristics are studied, and excellent device reliability is demonstrated. We compare the device performance of the fabricated capacitors with other stacked high-k MIM capacitors reported in recent literature.

Laser annealing experiments on commercially available phase pure tenorite (CuO) nanoparticles (NPs) were performed in air and nitrogen atmosphere to improve the structural and electronic properties, with respect to their suitability for photovoltaic applications. The particles exhibit size variations from about 30 nm to 100 nm. The influence of the thermal treatment is investigated by photoluminescence (PL) and Raman spectroscopy. Annealing of the particles in air by a laser treatment improved the material quality by defect reduction. Additional laser annealing in N2 atmosphere leads to a phase transition of the NPs from tenorite to cuprite (Cu2O). Due to the low partial oxygen pressure, the transition is initiated at about 1/3 of the maximum laser power used for the series in air, which is indicated by a drastic increase of the band edge emission from Cu2O. However, annealing with higher laser power leads to strong defect luminescence, which originates from copper and oxygen vacancies. A weak remaining tenorite band edge emission shows an incomplete phase transition.

Progress and challenges for chemical mechanical polishing (CMP) of GaN are discussed in detail by focusing on the importance of GaN surface oxidation during CMP. We report on the significant difference in the removal rates between Ga2O3 and GaN, suggesting that the surface oxidation reaction is the rate-limiting step for CMP of Ga-faced GaN. This is actually proved by the fact that ex-situ surface oxidation by annealing in air prior to CMP exhibits a marked reduction in the required CMP time to produce a damage-free surface. As a future challenge, we outline two of our recent developments, ultraviolet-assisted CMP and atmosphere-controlled CMP, that enable in-situ oxidation, since ex-situ oxidation must be modified to in-situ to further advance CMP.

Salt is the raw material of sodium metal, which reacts with water to produce hydrogen for power generation. Sodium metal is solid matter and its specific gravity is low; therefore, it can be stored or transported for long at room temperature and under atmospheric pressure as oil and coal can. Sodium metal is produced with molten-salt electrolysis from sea salt, lake salt or rock salt, and securely kept immersed in kerosene for preventing it from reacting with air or moisture when transported to a consumer place; where it reacts violently with water to generate a large amount of hydrogen instantly. And sodium hydroxide, which is a reaction residue obtained after the production of hydrogen, is supplied as it is as the raw material of soda industries. Moreover, fresh water, sulfuric acid, hydrochloric acid, sodium hydroxide, and magnesium are generated as by-products in the processes of manufacturing sodium metal and generating hydrogen. Sodium metal can be an alternative energy material for hydrogen combustion power generation, having a far-reaching economic effect.

Amphiphilic diacetylenes (DAs) can self-assemble into photopolymerizable liposomes that can be used to construct effective pathogen sensors. Here, modified commercial inkjet printers are used to disperse DAs into water, facilitating self-assembly. The liposomes are of similar size, but are significantly less polydisperse than liposomes formed using conventional sonication methods. The process is efficient, readily scalable and tolerant of structural modification. The derivitization of approximately 5% of the DA head groups and the incorporation of fluorophores into the hydrophobic bilayer allows for the preparation of novel multifluorophore PDA sensing systems that can provide enhanced bacterial discrimination in a single experiment by way of a fluorescent fingerprint.