Use of aluminum alloyed zinc oxide (AZO) as a transparent contact to p-GaN has received significant attention for GaN/InGaN light emitting diodes applications. Reports show that AZO as deposited on p-GaN forms a Schottky contact given the large work-function difference between AZO and p-GaN [1]. However, utilization of a thin nickel layer inserted between the AZO and p-GaN can result in an ohmic contact [2], given that Ni forms an ohmic contact to p-GaN upon annealing. Here, we undertake simulation studies of this AZO/Ni interface as a function of Nickel layer. Simulation studies of the transport mechanism in this contact indicate the likelihood of a tunneling junction at the AZO/Ni interface, thus the entire AZO/Ni forming an ohmic contact to p-GaN. Potential to better control injected current density uniformity utilizing such a contact structure is also discussed.

According to the recent hydrogen and methanol economy, the proton conducting materials appear very interesting as an electrolytic membrane and/or an electrode component of fuel cells, CO2/Syngas converters and water steam electrolysers. Prior to the long lifetime requirements their structural and mechanical behaviors as a function of operating condition: high temperature and high water vapor pressure, have to be well determined. Consequently, we designed the autoclave working till 620°C and 50 bars of H2O pressure equipped with a sapphire window allowing in situ Raman scattering measurements. It should be stressed that Raman scattering is an optical technique very efficient to detect both long and short range order structural modifications. The technical and scientific challenges/difficulties encountered during the studies performed on proton conducting zirconates are discussed.

To improve the conversion efficiency of polymer photodetectors (PDs) fabricated by solution process, the properties of fluorene-type polymer photodetectors doped with iridium (Ir) and platinum (Pt) complexes were investigated. The devices based on poly(dioctylfluorene) and poly(dioctylfluorene-co-benzothiadiazole) (F8BT) had violet and blue sensitivity, respectively. Triplet materials can enhance the incident-photon-to-current conversion efficiency of the devices utilizing the fluorene-type polymers when their triplet levels are lower than the lowest excited singlet states of the host and higher than the lowest excited triplet states of the host. The transmission of a moving picture was successfully demonstrated using the bilayer F8BT device with green Ir complex as an opto-electrical conversion device. We demonstrate that the polymer PDs fabricated by solution process can be applied to short-range optical communication fields, such as opto-electrical conversion devices for optical links.

Lead sulfide (PbS) nanoparticles (NPs) of different sizes (2.0 nm - 14.4 nm) have been synthesized in our laboratory. By using those NPs, we formed colloidal films on glass and GaAs substrates employing a specialized supercritical fluid CO2 (sc-CO2) deposition method. The deposited films contain only the PbS NPs and the protecting group of oleic acids and require no polymer matrix. The NP films are solvent free, environmentally stable, and show good adhesion to the substrates. The sc-CO2 deposition process can deposit films ranging in thickness from a few monolayers, in well ordered arrays, up to 0.5 μm or greater. The photoluminescence (PL) properties of these nano-structured films were studied with Fourier transformation infrared spectroscopy from 5 K up to 300 K.

Novel hydrogels composed of thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) and redox-responsive poly(ferrocenylsilane) (PFS) macromolecules were formed by photopolymerization. PFS chains bearing acrylate side groups were copolymerized with NIPAM and N,N’-methylenebisacrylamide in tetrahydrofuran in a predetermined ratio under ultraviolet light-emitting diode (UV-LED) irradiation at a wavelength of 365 nm, in the presence of a photoinitiator. Crosslinking occurred smoothly, providing homogeneous hydrogels. The equilibrium swelling ratio, rheology and morphology of these hybrid PNIPAM-PFS-based hydrogels were investigated. In-situ fabrication of silver nanoparticles inside the hydrogel network via reduction of silver nitrate by the PFS chains led to hydrogel composites. These composites showed strong antimicrobial activity while maintaining a high biocompatibility with cells.

A Mg(OH)2–C transparent conductive film was prepared using the sputtering method by the initial formation of a Mg-C film generated by the alternate layering of Mg and C on a rotating substrate and subsequent exposure of the film to atmospheric water vapor. To examine the influence exerted by the Mg/C layers of the starting film sample on semiconductivity,evaluations of the electrical conductivity properties of the film during the hydroxylation process and the optical properties after the hydroxylation process were carried out. As a result, although no effects on the characteristics of the electrical conductivity properties associated with the composition or number of layers in the films could be confirmed, it was determined that the films possessed the characteristics of semiconductors. On the other hand, the optical properties were found to be affected by the composition and number of layers of the Mg/C films.

The sintering of tantalum carbide nanopowders by spark plasma sintering (SPS) is investigated. The washing procedure for the powders is modified from previous work to eliminate excess lithium in the powders that is left over from the synthesis process. The sintering behavior of the nanopowders is investigated by X-ray diffraction and scanning electron microscopy by studying specimens that were sintered to different temperatures. To improve the homogeneity of the microstructure of the specimens, milling procedures were implemented. Vaporization during sintering is observed, and the usefulness of carbon additions and systematic decreases in temperature to curb this behavior was explored. Future experiments to achieve full density and to maintain a nanostructure of the specimens include sintering with higher pressures, lower temperatures, and longer dwell times. Additives for maintaining a nanostructure and developing suitable high-temperature properties are also discussed.

The microstructure change of the uranium-plutonium mixed oxide fuels (MOX fuels) irradiated in a fast reactor occurs because of a radial temperature gradient. To make detailed observations and elemental analyses of fuel samples, a field emission scanning electron microscope (FE-SEM) equipped with a wavelength-dispersive X-ray spectrometer (WDX) was installed in a hot laboratory.

Because fuel samples have high radioactivities and emit α-particles, the instrument was modified as follows :

1. 1) The instrument was attached to a remote control air-tight sample transfer unit between a shielded hot cell and the FE-SEM.

2. 2) The FE-SEM was installed in a lead shield box and the control unit was separately located outside the box.

After the installation, the microscopy and elemental analyses were applied to low burnup fuel samples. High resolution images were obtained and characteristic X-rays (U, Pu, and so on) emitted from the sample surface were measured. The technique has the great advantage of being able to evaluate the irradiated fuels in detail. In future work, samples of even higher radioactive will be observed and analyzed.

We report the synthesis, structural and optical characterization of PbSexS1-x nanorods with diameter between 2 nm to 4.5 nm and length of 12 nm to 24 nm. Their typical photoluminescence spectra exhibit a split of the band-edge exciton band. The temperature dependence photoluminescence of these nanorods revealed a relatively small band-gap temperature coefficient and a mild extension of the radiative lifetime at cryogenic temperatures - all in comparison with photoluminescence processes in PbSe nanorods, as well as in PbSexS1-x quantum dots, with similar absorption band-edge energy. A theoretical model associates the experimental observations to the occurrence of independent transitions from either degenerate or non-degenerate band-edge valleys in PbSexS1-x nanorods, each of which possessing a relatively small electron-hole exchange interaction.

Combinatorial phage display with a pVIII library of M13 bacteriophage was used to identify a peptide sequence capable of recognition and mineralization of copper sulfide. The six sequences isolated from the final biopanning round were rich in basic, hydrophobic, and polar amino acids compared to the phage display library. The peptide sequence, DTRAPEIV, was used to biomineralize copper sulfide on the pVIII major coat protein thus producing linear chains of nanoparticles. Electron microscopy revealed that the phage was capable of controlling the size of the nucleated nanoparticles in an aqueous solution at room temperature and that the mineralized material was copper sulfide. Phage-templated biomineralization is a low temperature, aqueous-based approach to synthesis of copper sulfide nanoparticles with hierarchical order.

The topic of this study is focused on exposure control measures and working practices to minimize/eliminate potential health, safety, and environmental risks associated with the handling of dry nanoparticles. First, it is shown that a glove box with attached vacuum chamber for material transport and air cleaning is highly effective in minimizing occupational exposure to airborne nanoparticles. Second, the propensity for Baytubes C 150 P multi-walled carbon nanotubes to form airborne particles is found to be very low. The combined results provide useful guidelines for both the selection and the use of an engineering control to minimize/eliminate exposure to airborne carbon nanotubes, and nanoparticles in general.

Bismuth has been used as an antimicrobial agent for treating gastrointestinal disorders, and has been used in the eradication of Helicobacter pylori. The aim of the present study was to analyze the antimicrobial activity of different Bi compounds against opportunistic pathogens. Ten bismuth compounds were tested with three different concentrations (60, 30 and 10%), against pure cultures of the following bacterial strains: Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Staphylococcus epidermidis. The results show that Bismuth subsalicylate, Bismuth trioxide and Bismuth subgallate had a good antibacterial activity however, Bismuth subsalicylate was the most effective in the inhibition of the four bacterial strains tested. In this study we confirm the antibacterial properties of Bi-based compounds for other bacteria than H. pylori.

In this study, ZnO f ilms heavily doped with Al or Ga were grown on a polarity-controlled buffer layer using pulsed laser deposition. The films prepared using a 1 mol% Al-doped target with the buffer layer grown at 700 °C had the c(+)-face, whereas the films with the buffer layer grown at 400 °C had the c(-)-face, which means that the polarity control can be successfully carried out using the buffer layer. However, the films prepared using targets doped with more than 1 mol% Al or Ga had the c(+)-face regardless of the polarity of the buffer layer. The 1 mol% Al-doped ZnO film with the c(+)-face had lower electron concentration and higher growth rate than the film with the c(-)-face. This result indicates that the Al content in the film with the c(-)-face was larger than that in the film with the c(+)-face.

Al/SiCp composites fabricated by the non-assisted infiltration route are attractive materials for various engineering applications. However, the presence of thermal stresses can impair their mechanical properties if they are utilized directly after processing. Therefore, heat treatments are potential solutions to this problem. In this work, the effect of T6-heat-treatment on the microstructure and hardness of Al/50% SiCp composites prepared by the non-assisted infiltration route is investigated. Previous to preform preparation, the SiC powders are coated with colloidal SiO2. Infiltration tests are conducted using two experimental Al-Si-Mg alloys. The composites are sectioned in specimen sizes of 1 cm2 and prepared using standard metallographic procedures. Then they are heat treated performing a solution treatment at 350°C for 3 h and artificial aging at 170°C for 1, 3 and 5 hours. In addition, the specimens are characterized by X-ray diffraction (XRD), optical microscopy, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). They are also characterized in hardness tests, comparing the behavior for the alloy with and without the various treatments. The results show that heat treatments do not affect the matrix/reinforcement interfacial condition and that the undesirable Al4C3 phase is not developed as consequence of thermal treatments. Hardness tests show that for alloy 1 the maximum hardness value is for the solution-heat-treated samples at 350°C and 5 h aging (28.26±4.02 HC); for alloy 2 the maximum hardness is achieved with solution heat treatment at 350°C and 3 h aging (25.86±4.05 HC). For composites processed with alloy1, the maximum hardness is obtained for the solution treated sample at 350 ° C for 3 h (91.8±2.17 HC), whereas for composites processed with alloy 2 the peak hardness is obtained in solution treated samples and aged at 170°C for 1 h (95.2±0.94 HC).

Field electron emission model of hydrogen-terminated n-type diamond was discussed. Ultra-violet photoelectron spectroscopy characterizations indicated that the electron affinity was -0.7 eV and an internal barrier of about 3.5 eV existed on the surface. Field electron emission properties depended on anode-diamond distances. Schottky barrier lowering model suggested that this internal barrier was lowered by the electric field (5.4x106 V/cm) applied onto the negative electron affinity surface of the H-terminated n-type diamond.

We have proposed the use of glass-like carbon (GC), as mold material because the 27-maximum etching selectivity of polysiloxane film against GC, which was approximately sixtimes larger than that of polysiloxane film against chemical vapor deposited (CVD) diamond film. We have investigated the fabrication of diamond nanopit arrays by room-temperature curing nanoimprint lithography (RTC-NIL) using GC mold, as applications to the emitter and the micro-gear. The polysiloxane has in the state of sticky liquid at room-temperature and negative-exposure characteristic. Therefore, the polysiloxane was used as RTC-imprint resist material, and also used as electron beam (EB) resist (oxide mask) material in EB lithography. We have fabricated the cylindrical GC nanodot mold with 500 nm-diameter, 600 nm-height and 2 μm-pitch. We carried out RTC-NIL using GC mold under the following optimum conditions: time from spin-coating to imprint of 1 min, imprinting pressure of 0.5 MPa and imprinting time of 5min. Then, we have processed the diamond film with an electron cyclotron resonance (ECR) oxygen ion shower. We have fabricated diamond nanopit array with 250 nm-depth and 500 nm-diameter. The diameter of diamond nanopit pattern was in good agreement with that of GC mold. Moreover, the depth of the diamond nanopit patterns fabricated by RTC-NIL using cylindrical GC mold was three times larger than that using conical diamond mold.

Continuous decrease of the feature size of transistors in modern integrated circuits (ICs) constrains thickness of auxiliary dielectric layers in interconnects because of their relatively high dielectric constant, which reduces the efficiency of low-k material integration. Dielectric materials used today as barrier or etch-stop layers are usually SiN (k ∼ 7.0) and SiCN (k ∼ 4.8), which k-value significantly exceeds that of recent ultra low-k materials (k < 2.2). In our work we have investigated thin films of rigid-chain polyimide (PI) with a k-value of about 3.2-3.3. This film was deposited using a Langmuir-Blodgett (LB) technique and can be as thin as several monolayers. The intermolecular interaction of densely packed precursor macromolecules within a monolayer formed at the water-air interface makes it possible to avoid penetration of precursor material inside the pores. The latter peculiarity of the deposition process results in a pore sealing effect using a 4 nm PI film.

Oxygen potentials of PuO2-x were measured at temperatures of 1473 - 1873 K by thermo-gravimetry. The oxygen potentials were determined by in situ analysis as functions of oxygen-to-metal ratio and temperature. The measurement data were analyzed on the basis of defect chemistry and an approximate equation was derived to represent the relationship among temperature, oxygen partial pressure, and deviation x in PuO2-x .

In this paper we report on the fabrication of n-doped ZnO and semiconducting n-ZnO at room temperature by a new ablation deposition technology that makes use of electron/plasma ablation sources named Pulsed Plasma Deposition (PPD) developed by Organic Spintronics Srl.

The oxygen vacancies n-doped ZnO PPD grown thin film is deposited on PET and shows a resistivity of 3 x 10-4ohm cm. The n-ZnO TCO is compact, smooth and highly transparent in the UV-VIS (better than 90 T%) as well as in the near IR spectral range and it is remarkably temperature stable. Typical ZnO deposition rate of the PPD is 500 nm/min.

The RT deposited semiconductor ZnO shows a very large Hall electron mobility up to 1000 cm2/Vs approaching that of the single crystal. Preliminary results of Si/SiO2 based bottom gate and contact FET test pattern structures with a 50 nm overlaying ZnO thin film shows an ON/OFF ratio of 50000 and a FET mobility of 1 cm2/Vs. Further implementation on appropriate FET design will be performed to explore the possibility to achieve a larger FET mobility. The PPD proves to be an enabling technology that makes it possible the advent of flexible OLED displays.