A multi-pressure microwave plasma source is developed and is applied for the fast deposition of crystalline silicon films. In this paper, the plasma source is diagnosed firstly. Electron density, electron temperature and discharge gas temperature of the plasmas generated in ambient air are studied using optical emission spectroscopy (OES) method. By using the high density microwave plasma source, depositions of crystalline silicon films from SiH4+He mixture at reduced pressure conditions are investigated systematically. After optimizing the film deposition conditions, highly crystallized Si films are deposited at a rate higher than 700 nm/s. We also find that the deposited films are fully crystallized and crystalline structure of the deposited film evolves along the film growth direction, i.e. large grains in surface region while small grains in the bottom region of the film. Based on the observed results, a possible mechanism, the annealing-assisted plasma-enhanced chemical vapor deposition, is proposed to describe the film growth process.

Thin films of magnetite (Fe3O4) are grown on a single-crystal Si/SiO2 (100) substrate with native oxide using DC reactive sputtering technique at room tempreture (RT) and 300C. The x-ray diffraction(XRD) result shows the thermal energy during deposition enhances the crystallization of the Fe3O4 and x-ray photoelectron spectroscopy confirms the film deposited at 300C is single-phase Fe3O4 while the film deposited at RT is mostly ν-Fe2O3. The electrical measurements show that the resistivity of the Fe3O4 film increases exponentially with decreasing temperature, and exhibit a sharp metal-insulator transition at around 100 K, indicating the Verwey transition feature. The saturation magnetization Ms of Fe3O4 film measured by vibrating sample measurement (VSM) at RT was found to be 445 emu/cm3.

Conductive nanofibers with the average diameters in the range of 60 nm - 2 μm were fabricated by electrospinning of a mixture of poly(3-hexylthiophene) (P3HT) and polyvinylpyrrolidone (PVP) in a mixed solvent of chlorobenzene and methanol. Beaded fibers and/or uniform, smooth-surface fibers were successfully fabricated. The average diameter of the as-spun fibers decreased and the color of as-spun fibers changed with decreasing the concentration of P3HT or PVP. After the removal of PVP from as-spun fibers by Soxhlet extraction, pure P3HT fibers were obtained as a spindle-like with groove-like morphological appearance which may be widely applicable for some specific applications, such as photovoltaic cells, thin film transistors, and light emitting diodes.

Epitaxial 3C-SiC was grown using an unconventional technique for epitaxial growth. Thin films of 3C-SiC were deposited onto the (111) and (110) faces of Si using pulsed DC sputtering of a high purity, hollow cathode SiC target. The films were studied using x-ray diffraction (XRD), reflection high energy electron diffraction (RHEED), transmission electron microscopy (TEM), and auger electron spectroscopy (AES) techniques. XRD results presented as Bragg diffraction spectra and pole figures, and electron diffraction patterns verify crystal orientation and epitaxy. In addition, AES profiles identify the compositional integrity of the deposited films.

In the current research, we successfully prepared TiO2/Ni–Cu–Zn ferrite composite powder for magnetic photocatalyst. The core Ni–Cu–Zn ferrite powder was synthesized using the steel pickling liquor and the waste solution of electroplating as the starting materials. The shell TiO2 nanocrystal was prepared by sol-gel hydrolysis precipitation of titanium isopropoxide [Ti(OC3H7)4] on the Ni–Cu–Zn ferrite powder followed by heat treatment. From transmission electron microscopy (TEM) image, the thickness of the titania shell was found to be approximately 5 nm. The core of Ni–Cu–Zn ferrite is spherical or elliptical shape, and the particle size of the core is in the range of 70–110 nm. The magnetic Ni–Cu–Zn ferrite nanopowder is uniformly encapsulated in a titania layer forming core-shell structure of TiO2/Ni–Cu–Zn ferrite powder. The degradation efficiency for methylene blue (MB) increases with magnetic photocatalyst (TiO2/Ni–Cu–Zn ferrite powder) content. When the magnetic photocatalyst content is 0.40 g in 150 mL of MB, the photocatalytic activity reached the largest value. With a further increase in the content of magnetic photocatalyst, the degradation efficiency slightly decreased. This occurs because the ultraviolet (UV) illumination is covered by catalysts, which were suspended in the methylene blue solution and resulted in the inhibition in the photocatalytic reaction. The photocatalytic degradation result for the relationship between MB concentration and illumination revealed a pseudo first-order kinetic model of the degradation with the limiting rate constant of 1.717 mg/L·min and equilibrium adsorption constant 0.0627 L/mg. Furthermore, the Langmuir–Hinshelwood model can be used to describe the degradation reaction, which suggests that the rate-determining step is surface reaction rather than adsorption is in photocatalytic degradation.

This article reports on the characterization of two- and three-layer ohmic contacts comprising of titanium disilicide and nickel silicide. Cross Kelvin resistor test structures were used to extract the specific contact resistivity (SCR) values for the different ohmic contacts fabricated. The SCR of aluminum to titanium silicide (Al-TiSi2) ohmic contacts was evaluated to be as low as 6.0 x 10-10 Ωcm2. Three-layer ohmic contacts were created using aluminum and nickel silicide thin films and doped silicon. SCR values as low as 5.0 x 10-9 Ωcm2 to antimony-doped silicon and 3.5 x 10-9 Ωcm2 to boron-doped silicon were evaluated.

We present a performance comparison of polythiophene/fullerene derivative bulk heterojunction solar cells fabricated on fluorinated tin oxide (FTO) and indium tin oxide (ITO) in the presence and absence of the commonly used poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) hole extraction layer. From a potential commercial perspective the performance of cheaper and more readily available FTO compares well with the more expensive ITO in terms of measured device efficiency (FTO:2.8 % and ITO:3.1%). The devices show similar fill factors (FTO:63% and ITO:64%) with the same open circuit voltage of 0.6 V. The short circuit current density is lower for FTO devices at 7.5 mA/cm2 which compares with 8.0 mA/cm2 for ITO; a behaviour that is mainly attributed to the reduced optical transmission of the FTO layer. Importantly, these devices were part fabricated and wholly characterized under atmospheric conditions. The quoted device performance is the best reported for FTO based bulk heterojunction systems in the absence of the highly acidic PEDOT:PSS hole extraction layer, which is believed to degrade conductive oxides.

The in-situ aqueous synthesis of ZnO nanorods doped with Sb is presented. To control the inclusion of Sb into the ZnO nanorods structure ethylene glycol (EG) is added to the reaction solution. The addition of EG reduces the rate at which Sb is included in the ZnO rods and produces nanorods with a morphology that is similar to the undoped rods. This is contrary to the rods produced with Sb in the absence of EG which produce a less well ordered structure. An I/V curve taken from individual rods indicates a change in the diode behaviour. The change in I/V behaviour is associated with a change from the natural n-type behaviour of ZnO to a p-type behaviour due to the Sb doping.

Following containment failure in the scenario of geological disposal of spent nuclear fuel, the penetration rate of groundwater into the UO2 matrix could cause a rapid increase of the fraction of inventory becoming available for prompt dissolution. In this respect, oxygen and water diffusion mechanisms are key issues to investigate. In this work, secondary-ion-mass-spectrometry (SIMS) depth profiling has been applied to characterize a polycrystalline UO2 pellet exposed to 18O-labelled water at room temperature. 18O depth profiling up to 25 μm beneath the pellet surface clearly indicates a combination of oxygen diffusion into the UO2 lattice and water diffusion along grain boundaries, behaving as high diffusivity paths. The lattice diffusion coefficient of oxygen, DL , and the quantity δDB – product of the grain boundary width, δ, and the grain boundary diffusion coefficient of water, DB – have been measured, resulting in DL = (2.5 ± 0.1) × 10-24 m2 s-1 and δDB = (7.5 ± 0.3) × 10-24 m3 s-1.

Thermoluminescence (TL) properties of pulverized SiO2:V monoliths synthesized by a solgel method, and annealed at 1273 K during 12 h under air, are presented in this work. Characteristics TL glow curves display a complex shape with at least three maxima located at ˜379, ˜543 and ˜591K. The TL total signal exhibited a linear behavior for doses below 400 Gy. The integrated TL fades down 26 % after 3 h elapsed between irradiation and the corresponding TL readout. These results lead to conclude that annealed SiO2:V is a promising material for ionizing radiation detection and dosimetry.

We have investigated the possibility of using the protease enzyme thermolysin to catalyse the synthesis and gelation of ionic-complementary peptides from non-gelling peptide precursors. In the described system, thermolysin was added at a fixed concentration (0.3 mg mL−1) to solutions (25 - 100 mg mL−1) of a short tetra-peptide FEFR. Initially, the protease partially hydrolysed the tetrapeptide into di-peptides in all samples. Subsequently, longer peptide sequences were found to form through reverse-hydrolysis and their stability was found to be dependent on their self-assembling properties. The sequences that self-assembled into anti-parallel β-sheet rich fibres became the stable products for the reverse hydrolysis reaction, while the others formed were unstable and disappeared with increasing incubation time. Ultimately, the main product of the system was octa-peptide, which suggests that it represents the thermodynamically favoured product of this dynamic library.

Superparamagnetic iron oxide nanoparticles coated with natural polymers have found many applications in the field of biosensors as magnetic carriers due to the combination of two characteristics: the possibility of controlling the particles movement by applying external magnetic fields and attaching biomolecules to the particle through a chemical bond. The aim of this work was to prepare long-term stabilized particles with acid groups available to be used as magnetic carriers of biomolecules. In this study, we present the synthesis of maghemite nanoparticles coated with alginate, a natural polymer. Particles were characterized by electron microscopy. Magnetic properties were studied by vibrating sample magnetometry, which revealed the superparamagnetic behavior of maghemite nanoparticles. Horseradish peroxidase (HRP) was chemically bonded to the maghemite-alginate particles and the enzymatic activity of HRP was determined by a colorimetric technique. The maghemite-alginate particles were immobilized onto the surface of a gold electrode by means of a magnet and the HRP activity was followed electrochemically, showing that these particles can be successfully used in amperometric sensors. Furthermore, maghemite-alginate particles were also used for the diagnosis of the foot-and-mouth disease by means of an enzyme-linked immunoassay with electrochemical detection. 3ABC protein, a non-structural protein of the virus, was linked to the maghemite-alginate particles and used to selectively detect anti-3ABC antibodies in cattle sera.

Austenitic stainless steel HK40 is heat-resistant steel, which is used at high temperatures, used mainly in the form of castings poured by gravity into tubes used in chemical process equipment, metallurgical, petrochemical, steel therefore must resist this oxidation, carburization and sulfatation. One problem in this type of steel is the formation of brittle phases, when subjected to a temperature of 540–900 °C. The aim of this study is to determine the possible presence of M7C3 type carbide, M23C6. The tube has an outside diameter analyzed 4 inches (10.16 cm) and a wall thickness of 0.5 inches (1.27 cm). The samples used for this investigation were cut 5 specimens measures 12.5 mm in diameter and 2.25 mm in length, and underwent a heat treatment at a temperature of 680 °C for 15, 30, 45, 60 and 75 minutes with subsequent cooling in water. The samples were characterized by electron microscopy. This study was performed because the trend in the Petrochemical Industry is to reduce the wall thickness of the tubes to improve heat dissipation and reduce the residual stresses generated in the steel.

The present work reports the photodegradation results of the Reactive Black 5 (RB5) izo dye by using titanium oxide films as photocatalysts. The films were obtained by ultrasonic spray pyrolysis deposit technique from a 0.0076 M of Ti(IV)-acetyl-acetonate and N, Ndimethylformamide solution over corning glasses as substrates. The film obtained by deposition at 450 °C for 6.0 min shows the best photocatalysis behavior, which may degrade 50% of 100 ppm RB5 in a period of 120 min, as monitored with a spectra-photometer UV-Vis between 190 to 900 nm. After 180 minutes of degradation, a 70% conversion could be obtained. These results are better than that obtained with TiO2 powders as photocatalyst.

In this work, 4H-SiC substrates intentionally misoriented from the (0001) plane toward [1-100] direction are shown to eliminate rotational twinning in icosahedral boron arsenide (B12As2, abbreviated here as IBA) epitaxial films. Previous studies of IBA on other substrates, including (100), (110), (111) Si and (0001) 6H-SiC, produced polycrystalline and twinned epilayers. Comparisons of IBA on on-axis and off-axis c-plane 4H-SiC by synchrotron white beam x-ray topography (SWBXT), and high resolution transmission electron microscopy (HRTEM) confirm the single crystalline and much higher quality of the films on the latter substrates. Furthermore, no intermediate layer between the epilayer and substrate was observed for IBA on off-axis 4H-SiC. Steps formed on the off-axis 4H-SiC substrate surface before deposition cause the film to adopt a single orientation, a process that is not seen with substrates with either no misorientation, or those tilted toward the [11-20] direction. This work demonstrates that c-plane 4H-SiC with 7° offcut toward (1-100) is potentially a good substrate choice for the growth of high-quality, untwinned B12As2 epilayers for future device applications.

A quasi-solid-state dye-sensitized solar cell is presented, where the conventional liquid electrolyte is replaced by an electrolyte film, reaching a solar light-to-current conversion efficiency of 3%. Contactless transient photoconductance measurements were performed, revealing decay behavior of photoinduced charge carriers, dependent on external applied potential conditions. The measurements show that the decay is controlled by the injection of electrons into the front contact, hindered or enhanced by the field in the space charge region.

This article focuses on mechanistic aspects of hyperthermal atomic oxygen reactions with polymers, which are the major contributor to material degradation in low Earth orbit. Due to the importance of well-controlled experiments in the understanding of the reaction mechanisms, ground-based experimental results obtained by a hyperthermal atomic oxygen beam generated by laser detonation facilities are mainly surveyed. Combined effects of atomic oxygen and vacuum ultraviolet (VUV) light on fluorinated polymers are also described. Such combined effects of hyperthermal atomic oxygen and VUV light are important not only from a fundamental point of view but also for engineering purposes (i.e., methodology for ground-based space environmental simulation). The VUV-sensitive polymers, poly(methyl methacrylate), and Teflon fluorinated ethylene-propylene do not show significant synergistic effects. Instead, the effect of combining atomic oxygen and VUV light produces erosion of the polymer that is the sum of the erosion caused by atomic oxygen and UV light acting individually. The experimental results suggest that material erosion in a complicated space environment may be quantitatively predicted if the erosion yields caused by the individual action of atomic oxygen and VUV light are known.

A study of the impact of surface preparation and post-deposition annealing on contact resistivity for sputtered Ni and Co contacts to thin film Bi2Te3 is presented. The contact resistance values obtained using the transfer length method (TLM) for Ni is compared to Co as a potential contact metal to Bi2Te3. Post-deposition annealing at 100°C on samples that were sputter cleaned reduces the contact resistivity to < 10-7 Ω-cm2 for both Ni and Co contacts to Bi2Te3. Co provided similar contact resistance values as Ni, but had better adhesion and less diffusion into the thermoelectric (TE) material, making it a suitable candidate for contact metallization to Bi2Te3 based devices.