Ti-Si-N nanocomposite coatings have been investigated using a hybrid coating system. The elimination of macro particles and the control of Si content should be accompanied to realize high quality of coating layer since macro particles induce corrosive reaction and the Si content of Ti-Si-N coating affects the mechanical properties such as hardness and friction coefficient. We introduced the hybrid coating system which consists of double bending filtered vacuum arc system (DBFVAS) and magnetron sputter cathode to solve two problems such as the macro particles and the control of Si content in Ti-Si-N coatings. The DBFVAS and magnetron sputter equipped with Ti cathode and Si cathode target, respectively. Ar and N2 are used for discharge and reaction gas and operating pressure is 0.6 mTorr. We confirmed that the DBFVAS reduced macro particles effectively and the Si content could be changed by controlling the applied power on magnetron sputtering cathode. The properties of Ti-Si-N coating layer are estimated by X-ray diffraction, X-ray photoelectron spectroscopy, wear test and nano indentation. And we compared Si content with Si emission (594.84 nm) of process chamber using an optical emission spectroscopy.

Epitaxial growth of a NiSi2 layer was observed on S+ ion-implanted Si(100) at a low temperature of 550 °C. Depending on the S+ dose and the Ni thickness, we identified different nickel silicide phases. High quality and uniform epitaxial NiSi2 layers formed at temperatures above 700 °C with a 20-nm Ni on high dose S+ implanted Si(100), whereas no epitaxy was observed for a 36-nm Ni layer. We assume that the presence of sulfur at the silicide/Si(100) interface favors the nucleation of the NiSi2 phase. The S atom distributions showed ultrasteep S depth profiles (3 nm/decade) in the silicon, which results from the snow-plow effect during silicidation and the segregation of S to the interface due to the low solubility of S in both Si and the silicide.

In this paper, we report on the preparation and applications of nanofiber networks, particularly in the area of optelectronics. The major topics are (i) carbon nanotubes grown on carbon nanofibers for a field emitter, (ii) dye-sensitized ZnO nanowires grown on carbon nanofibers for a photoelectrochemical cell, (iii) nanofiber coatings for coloring, and (iv) nanofiber coatings on gold substrate for surface plasmon resonance. The results presented here reveal the potential use of nanofiber networks for various optoelectronic devices.

Two dimensional photonic crystal (PhC) microcavity structures were fabricated using epitaxial ferroelectric thin film as the optical media and their resonant optical properties were measured. The PhC structures are utilized in order to achieve strong light localization to enhance the interaction between the incident light and the nonlinear optical barium titanate (BTO). Fluorescence measurements were used to assess the resonant properties. Two types of resonant structures were investigated consisting of either dopant or vacancy PhC arrays. The nano patterning on BTO thin films was achieved using dual beam focused ion beam (FIB). For the dopant type PhC microcavity structure, a larger air hole is generated in every 5 x 5 unit cells forming a super cell. The spatial profiles of PhC microcavity structures are characterized by laser scanning confocal microscopy. Structures with a feature size approaching the optical diffraction limit are clearly resolved. Fluorescence measurements on PhCs coated with a fluorescent dye were carried out to determine the relationship between the degree of light localization and the photonic band structure. Enhanced fluorescence at wavelengths 550-600 nm is observed in the dye covered PhCs with lattice period a =200 nm and a =400 nm. The large fluorescence enhancement results from the presence of PhC stop bands that increase the emission extraction efficiency due to the strong light confinement. Since the only allowed propagation direction for the scattered fluorescence light is out-of-plane, this enhances the vertically fluorescent extraction efficiency. These BTO optical microcavity structures can potentially serve as active nano-photonic components in bio-sensors and integrated photonic circuits.

This paper pursed one new cost effective strategy to improve the photocatalytic activity of the sol-gel developed Zn doped TiO2 by mechano-chemically milling in high energy planetary mill. The results showed that the photocatlytic activity was improved two times due to the increase of the surface area and the decrease in average crystallite size at the same time after using the high energy ball milling. Kubelka-Munk spectra of pristine and ball milled samples revealed a blue shift from 3.2 eV to 3.35 eV, which may be because of the presence of quantum size effects. SEM microstructural investigations revealed variations in the surface morphology with different Zn doping concentrations in the TiO2-Xwt.% Zn nanoparticulates. EDS spectra of these samples confirmed the stoichiometric concentration of Zn. Other characterization including X-ray diffraction (XRD), BET surface and the photocatalytic decomposition were also studied and the results were in agreement with each other.

In this work, we investigated the evolution of Silicon Nanostructures with progressive annealing under different growth conditions. A structure - SixNy/a-Si/SixNy/a-Si - was grown on n-type <100> Silicon substrate using Hot Wire CVD (HWCVD) deposition technique. We report here the growth of Silicon Nanostructures by HWCVD technique with a special focus on the nature and morphology of the nanostructures with variation in growth rate and post-annealing temperature. AFM studies revealed promising results hinting at the presence of Silicon Nanostructures. With progressive annealing the morphology of the Nanostructures changed from particles to sharp pillars particularly in one of the samples elaborated in the text below. FWHM from the Confocal Raman data at room temperature was found to be 3.19 cm−1 with the a-Si peak at 520 cm−1.

We report our investigations of large area multi-junction solar cells based on hydrogenated nano-crystalline silicon (nc-Si:H). We compared results from cells deposited by RF (13.56 MHz) at lower deposition rate (˜3 Å/s) and by Modified Very High Frequency (MVHF) at higher rate (≥ 10 Å/s). With optimized process conditions and cell structures, we have obtained ˜12% initial small active-area (˜0.25 cm2) efficiency for both RF and MVHF cells and 10˜11% large aperture-area (˜400 cm2) encapsulated MVHF cell efficiency for both a-Si:H/nc-Si:H double-junction and a-Si:H/nc-Si:H/nc-Si:H triple-junction structures on Ag/ZnO coated stainless steel substrate.

In order to evaluate the radiation response of 12YWT nanostructured ferritic steel to high dose neutron irradiation, the solute distribution, and size, number density, and compositions of nanoclusters in the unirradiated condition and after neutron irradiation to a dose of 3 dpa at a controlled temperature of 600 °C were estimated by atom probe tomography. No statistical difference in the average size or size distribution of the nanoclusters was found between the unirradiated and irradiated conditions. Therefore, these nanostructured ferritic steels are promising candidate materials for use under extreme conditions in future generations of advanced reactors.

InP-based HBTs for ultrahigh speed optical communications systems operation at over 40 GHz require a long-term stability under high current injection conditions, such as current densities of 2 or 5 mA/μm2. We achieved high reliability by suppressing surface recombination and emitter-metal-related crystalline degradation.

Changes in the electric properties of devices due to temperature and bias stress were evaluated. The reduction in DC current gain due to surface recombination had the activation energy of 1.7 eV without current density dependence, and the lifetime of HBTs for this degradation mode is predicted to be over 1×108 hours at 125°C. The emitter metal diffusion and disruption of uniformity of the atomic composition were observed by transmission electron microscopy and energy dispersive X-ray spectroscopy in HBTs with the conventional Ti/Pt/Au emitter, whereas suppression of those degradations was observed in HBTs with refractory metal of Mo and W. The emitter resistance was estimated to evaluate the contact layer degradation. The critical time was one order larger for HBTs with refractory metal than for HBTs with conventional metal. The activation energies for resistance increases were 2.0 and 1.65 eV for the current density of 2 and 5 mA/μm2, respectively, for all types of emitter electrodes.

The effectiveness of the refractory metal electrode for improving device reliability was confirmed, especially in high-current-density operation, which is essential for applying InP HBTs in high-speed ICs.

The TRISO fuel that is intended to be used for the generation IV nuclear reactor design consists of a fuel kernel of Uranium Oxide (UOx) coated in several layers of materials with different functions. One consideration for some of these layers is Silicon Carbide (SiC) [1]. The design, manufacture and fabrication of SiC are done at the Center for Irradiation of Materials (CIM). This light weight material can maintain dimensional and chemical stability in adverse environments and very high temperatures. The characterization of the elemental makeup of the SiC material used is done using X-ray photoelectron spectroscopy (XPS). Nano-indentation is used to determine the hardness, stiffness and Young's Modulus of the material. Raman Spectroscopy is used to characterize the chemical bonding for different sample preparation temperatures.

The early stage formation mechanisms operating during the sublimation growth of CdTe films on CdS has been evaluated using a growth interrupt methodology for deposition under 100 Torr of N2. Key stages of the growth were identified and are discussed in terms of the processes of island nucleation, island growth/coalescence, channel formation and secondary nucleation that have been reported for other materials systems. It was demonstrated that the grain size could be manipulated by means of controlling the gas pressure in the range 2 – 200 Torr, with the grain diameter increasing with pressure linearly as D (μm) = 0.027(± 0.011) × P (Torr) + 0.90(± 0.31). For a series of solar cells made using such material, the performance parameters were seen to increase with grain size up to a plateau corresponding to grains of ∼4 μm in this case. Equivalent circuit parameters for resistive components arising from grain boundaries, and the contact to the CdTe, were measured. It is considered that grain boundary barriers in CdTe are harmful to PV performance, and that the plateau in performance occurs when the grain size is increased to the level where the contact resistance is greater than that due to grain boundaries.

Metallic and non-metallic nanoparticles, usually supported on non-metallic substrates have attracted much interest concerning their application in the field of electrocatalysis. To characterize catalysts with respect to size, morphology, structure and composition (alloys or core-shell) of nanoparticles and their associated electrocatalytic activity, transmission electron microscopy (TEM) is the state of the art method. This investigation shows the advantages of advanced image processing using the local adaptive threshold (LAT) routine.

GaAs based metamorphic and pseudomorphic high electron mobility transistors (HEMTs) under DC and thermal stress were studied. InAlAs/InGaAs MHEMTs grown on GaAs substrates were stressed at a drain voltage bias of 2.7V for 36 hours as well as thermally stressed at 250°C for 36 hours. Under both stress conditions, the drain current density decreased about 12.5%. The gate current, however, increased more after the thermal storage as opposed to DC bias. Reaction of the Ohmic contact with the underlying semiconductor was the main cause of degradation after thermal stressing. Transmission electron microscopy verified that gate sinking occurred in devices that underwent DC bias stressing. InGaAs pHEMTs that received a 1000 hour lifetime stress test from a commercial vendor showed similar degradation as virgin devices when stressed under DC bias for 24 hours. Virgin devices that were thermally stressed while undergoing DC bias showed minimal degradation up to 120°C, but exhibited catastrophic failure at 140°C.

Degradation processes in high power broad-area InGaAs-AlGaAs strained quantum well lasers were studied using electron beam-induced current (EBIC) techniques, time-resolved electroluminescence (TR-EL) techniques, and deep-level transient spectroscopy (DLTS). Accelerated lifetests of the broad-area lasers yielded catastrophic failures at the front facet and also in the bulk. EBIC was employed to study dark line defects generated in degraded lasers stressed under different test conditions. TR-EL was employed to study the intra-cavity intensity distribution in real time as devices were aged. DLTS was employed to study deep electron traps in both pristine and degraded laser diodes. Lastly, we present a possible scenario for the initiation of bulk degradation in the broad-area lasers.

Two donor-acceptor copolymers containing perylene diimide and oligothiophenes linked through triple bonds have been designed and synthesized by palladium catalyzed Sonogashira coupling reaction. The introduction of the triple bond spacer between the electron-acceptor perylene moieties and the electron donating oligothiophene moieties produces an extended conjugation along the main chain, and produces soluble and high molecular weight copolymers.The thermal, optical and electrochemical properties of these copolymers were examined. The HOMO-LUMO energy levels of these copolymers, along with the photoinduced charge transfer process, probed by photoluminescence quenching and by FTIR photoinduced absorption spectroscopy, in blends with poly(3-hexylthiophene) (P3HT), indicate that they are suitable materials for application as electron acceptor and n-type components in bulk heterojunction solar cells with P3HT.

In this report, we describe recent efforts in fabricating new nanocarbon-supported titanium dioxide structures that exhibit high surface area and improved electrical conductivity. Nanocarbons consisting of single-walled carbon nanotubes and carbon aerogel nanoparticles were used to support titanium dioxide particles and produce monoliths with densities as low as 80 mg/cm 3. The electrical conductivity of the nanocarbon-supported titanium dioxide was dictated by the conductivity of the nanocarbon support while the pore structure was dominated by the titanium dioxide aerogel particles. The conductivity of the monoliths presented here was 72 S/m and the surface area was 203 m2/g.

We studied the nucleation and crystallization of sol-gel derived (Ba0.7Sr0.3)TiO3 [BST(70/30)] thin films at low temperatures between 500 to 600°C on Pt(111)/TiO2/SiO2/Si substrates by a process using a combination of 2-ethyl-hexanoate based solutions and modified film preparation. We found that BST films could be crystallized at 500°C and that the films obtained had a columnar-like grainy microstructure with favorable electrical characteristic such as high relative permittivity (ɛr) of 310 at 10 kHz and high tunability of 51% at a bias electric field of 250 kV/cm. Moreover, we investigated annealing temperature dependence of BST(70/30) thin films. The results indicated er and tunability increased with annealing temperature up to 450 and 58%, respectively.

The polylactic acid (PLLA) is commonly used in the biomedical application. The physical and mechanical properties of PLLA depend on the molecular weight, crystallinity, and synthesis. In this work, we study the PLLA crystallization kinetics. One of the main attractive of these polymers is that its degree of crystallinity can easily be modified, from amorphous state to a high crystallinity degree. In this study a new technique is applied to follow the crystallization kinetic. An optical microscope with cross polarizers, warming plates and video camera were used. A series of images were obtained under isothermal conditions to observe the growth spherulite. Since an image is composed by pixels and each pixel has a value from 0 to 255, which represents gray intensity, being zero for black and 255 are white. Then, the pixels average versus time was plotting and from the plots crystallization kinetic and secondary crystallization are easily obtained.

This work presents recent results on outdoor characterisation of high efficiency luminescent solar concentrators. Outdoor measurements at 25�C and corrected to 1000 W/m2 have been compared with indoor characterization according to the international standards for conventional photovoltaic devices. Dependence of electrical parameters with temperature is also shown, together with results of various 1-day monitoring campaigns of luminescent concentrators performance under varying irradiance conditions. Results highlight the importance of those devices as potentially cheap, residential concentrating systems.

High-resolution synchrotron radiation X-ray photoelectron spectroscopy (HRXPS) is used to study the chemical bonding at the Al2O3/Si(001) and Al2O3/Si(111) interfaces. In both cases, the Si2p spectra recorded at 180 eV photon energy provides evidence a thin interfacial layer rich in Si-O bonding. On the other hand, conventional AlKα X-ray source angular measurements clearly indicate that there are two in-plane orientations for Al2O3/Si(111) : [11-2]Al2O3(111)//[11-2]Si(111) and [-1-12] Al2O3(111)//[11-2]Si(111) but four in-plane orientations for Al2O3/Si(001) : [11-2] Al2O3(111)//[100]Si(001), [11-2]Al2O3(111)//[010]Si(001), [11-2]Al2O3(111)//[-100]Si(001), and [11-2]Al2O3(111)//[0-10]Si(001).