In this paper, the authors introduce and present some findings on an alternative non-contact material removal technique. Material removal is made possible by utilizing the electrokinetic and hydrodynamic effects of suspended particles to manipulate their trajectories to impact onto the surface of the workpiece. The research was previously demonstrated and reported where the removal rate can be precisely controlled by varying the electrical field and the flow rate of the slurry across the surface of the workpiece. New findings are reported on the application of the technique to different materials that will highlight the attractiveness of this alternative approach to producing surfaces with roughness in the order of nanometres.

We present an optoacoustic method to non-destructively measure the average dimensions of a periodic array of simple structures with aspect ratios greater than 10:1, which are inaccessible to AFM techniques. The technique that we describe could be used as the basis of an inline metrology tool for wafer inspection. The samples examined were test structures with high precision lithographically defined lines of silicon dioxide deposited on a silicon substrate. The thickness of the silicon dioxide was around 400 nm, and the gaps between the lines ranged from 100 nm down to smaller than 40 nm. A drop of water was placed on the sample, and an optoacoustic transducer was placed on top; measurements were taken with a water thickness less than 1 micron between the optoacoustic transducer and the sample. The water filled the spaces between the lines due to the hydrophilic nature of the sample surface. Using the picosecond ultrasonics technique, acoustic pulses are generated in a special optoacoustic transducer, transmitted through a coupling fluid (water), scattered off of the sample being examined and then return to the transducer. The returning acoustic signal shows nanometer sensitivity to the height of the lines and the specific details of their profile.

This article underlines with examples of studies for energy related materials and processes how important and useful the technique of neutron imaging can be for our future energy supply. With the help of the particularly designed configurations for each such study it becomes possible to derive essential information for the material properties and their change in a non-invasive manner.

The four mentioned examples (PEM fuel cell, Li-battery, hydrogen storage and nuclear fuel inspection) cover a very wide range of applications and demonstrate the high potential of the various used methods in neutron imaging.

Photoluminescence (PL) spectroscopy of nanocrystalline TiO2 using ultraviolet light excitation reveals a range of intra-bandgap defect states which emit at visible wavelengths. In this study we use 350 nm excitation to probe the luminescent defect states of TiO2 nanotubes fabricated by anodization of titanium. The nanotubes show a broad visible luminescence from 450 to 700 nm with a peak at 520-550 nm or 2.4-2.3 eV. The intensity of nanotube PL is orders of magnitude lower than that of nanoparticulate anatase and P25 (mixed-phase anatase/rutile) films of comparable thickness. Similar to the PL of the nanoparticles, the nanotube PL is increased by vacuum annealing. The nature of the nanotube defects is investigated through shifts in the intensity and shape of the PL spectra in hole or electron scavenging environments. We find the PL intensity of the nanotubes to be less dependent on environment than that of conventional TiO2 nanoparticles. We conclude that there are two inter-related reasons for decreased intensity and decreased environmental dependence of PL from TiO2 nanotubes as compared to nanoparticles: decreased density of defect states and improved carrier transport.

Metallic nanoparticles may be tailored to obtain specific size and morphology. In this work we present the synthesis of Ni/TiO2 catalysts by a photodeposition method. Our investigation included the photochemical and photocatalytic reduction of the nickel organometallic precursor (Ni (II) acetylacetonate) over titania (Degussa P-25) support. The photo-reduction kinetics was followed by UV-Vis and the catalysts were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). According to the results, the photochemical reduction of the Ni precursor was only 30% at λ= 254 nm, whereas, the photocatalytic route was approximately 90 % (λ= 365 nm) yielding Ni nanoparticles with diameter ranging from 10 to 40 nm.

Graphene is generating a considerable interest in materials science and condensed-matter physics. One crucial technological problem, that will govern future applicability of this material, is related to the patterning of graphene while preserving the exceptionally high crystallinity and electronic properties of this material. This article is aiming at demonstrating that a highly focused beam of gallium ions can be applied for sculpting ultra-thin and high quality suspended graphene nano-ribbons (GNRs).

Membrane separations are a key enabling technology for future energy conversion devices. Ionic transport membranes must have both proton and electronic conductivity to function as hydrogen separation membranes without an external power supply. A technical obstacle to material modification by compositional changes is that the hydrogen flux through a dense membrane is a function of both the proton ionic conductivity and the electronic conductivity. An alternative way to modify the materials conductivity without changing the ratio of the chemical constituents is by altering the microstructure. In this study, SrCe0.95Yb0.05O3 was produced by conventional mixed oxide bulk ceramic techniques and chemical solution routes self-rising approaches using urea as the leavening agent. In conventional ceramic processing routes, the perovskite phase was observed to form at temperatures near 1300oC, while solution techniques resulted in perovskite phase formation starting near 1000oC with complete phase transformations occurring at 1100oC. Thermogravimetric analysis (TGA) was conducted in various gas atmospheres resulting in bulk oxide route powders exhibiting a 0.6% weight loss at 800oC under a nitrogen environment as compared to chemically derived powders which displayed weight losses on the order of 3.4%.The increased weight loss observed in chemically derived SrCe0.95Yb0.05O3 is correlated with an increase in the number of electron charge carriers and results in elevated electronic conduction. This study will report on the development of structure property relations in the model proton conducting ceramic system SrCe0.95Yb0.05O3.

In the present work, silicon nitride nanowires (SNNWs) have been synthesized via nitriding cryomilled nanocrystalline silicon powder. The silicon powder exhibits a fine polycrystalline structure after the cryomilling process, with an average grain size of 25 to 125 nm at various cryomilling times. The SNNWs that form after the nitridation of the cryomilled silicon powder exhibit single crystal structure and are 20 to 100 nm in diameter and ∼10 µm in length. The diameter of the nanowires is in agreement with the grain size of the cryomilled Si powder. Microstructural characterization reveals that the as-synthesized nanowires have a hexagonal structure and their primary growth direction is along the [0001] direction. The formation of the Si–N–Si bond during the cryomilling process, as investigated theoretically with density functional theory, promotes the subsequent synthesis of the α-Si3N4 nanowires. The mechanism for nanowire formation appears to be a vapor-solid (VS) reaction.

We present a systematic study of semiconductor and dielectric properties as a function of annealing treatments at CCTO thin films deposited by pulsed laser deposition at 720 °C in 200 mTorr oxygen. The as-deposited thin film samples contain a high concentration of defects that contribute to the semiconductivity in the interior of grains. With increasing annealing temperature, the apparent dielectric constant decreases, and the resistance increases, both at a given temperature (e.g. room temperature). After annealing at 680oC, the semiconductivity was almost completely suppressed and CaCu3Ti4O12 behaved as a dielectric material. Knowing that oxygen vacancies are removed during annealing, one can infer that the dopant states are related to oxygen vacancies. A double plateau behavior in the dielectric constant vs temperature graph indicates that there are at least two defect levels in CaCu3Ti4O12 thin films. This was confirmed by simulating the capacitance response of a Schottky barrier containing two defect levels. Apart of the usual acceptor level, a trap at 500 meV from the valence band was identified. The finally achieved quasi intrinsic material exhibits a negative temperature dependency of the dielectric constant below 120 K.

Solution-processable organic bulk-heterojunction photovoltaic devices have made great advances over the past decade. The concept, ultrafast photo induced electron transfer from a conjugated polymer to fullerene derivative molecules in bulk-heterojunction systems, leads to device efficiencies as high as 6%. Light absorption, charge separation and charge transport to electrodes are the most important steps in organic photovoltaic devices. The enhanced light absorption through thicker active layers results in more exciton creation, however, leads to increased recombination due to the relatively short exciton diffusion length. We fabricated poly(3-hexylthiophene)/ [6,6]-phenyl C61 butyric acid methyl ester bulk-heterojunction devices with multiwall carbon nanotubes in the active layer in a bid to address this deficiency. Functionalization of carbon nanotubes allows better dispersion in aromatic solvents, 1,2-dichlorobenzene in this study, and pristine multiwall nanotubes result in poorer dispersions. Organic photovoltaic devices fabricated with pristine multiwall carbon nanotubes in the active layer result in power conversion efficiencies ˜1.4%, which show localized nanotube-rich areas in the active layer. Alternatively, acid functionalized nanotubes in the active layer results in efficiencies as high as 2.2 % with no distinct nanotube-rich sectors. The open circuit voltages of the devices show a dependency on the loading of nanotubes in the active layer. Further, the shunt resistances of the devices with carbon nanotubes decrease, which needs careful selection of the tubes depending on active layer thickness. This work compares the device performances in detail and identifies further improvements to conjugated polymer/fullerene derivative/multiwall carbon nanotubes hybrid photovoltaic systems.

Amorphous silicon single-junction p-i-n and Micromorph tandem solar cells are deposited in KAI-M reactors on in-house developed LPCVD ZnO front TCO's. An a-Si:H p-i-n cell with a stabilized efficiency of 10.09 % on 1 cm2 has been independently confirmed by NREL. An alternative ZnO/a-Si:H cell process with an intrinsic absorber of only 180 nm has reached 10.06 % NREL confirmed stabilized efficiencies as well. Up-scaling of such thin cells to 10x10 cm2 mini-modules has led to an aperture module efficiency of stabilized 9.20 ± 0.19 % as well independently confirmed by ESTI of JRC Ispra.

Micromorph tandem cells with stabilized efficiencies of 11.0% have been achieved on as-grown LPCVD ZnO front TCO at bottom cell thickness of just 1.3 μm in combination with the in-house developed AR concept. Applying an advanced LPCVD ZnO front TCO stabilized tandem cells of 10.6 % have been realized at a bottom cell thickness of only 0.8 μm. Implementing in-situ intermediate reflectors in Micromorph tandems on LPCVD ZnO reached in a stabilized cell efficiency of 11.3% with a bottom cell thickness of 1.6 μm.

The critical factor that limits the efficiencies of organic electronic devices is the low charge carrier mobility which is attributed to disorder in organic films. In this work we study the effects of active film morphology on the charge transport in Organic Field Effect Transistors (OFETs). We fabricated the OFETs using different substrate temperature to grow different morphologies of C60 films by Hot Wall Epitaxy. Atomic Force Microscopy images and XRD results showed increasing grain size with increasing substrate temperature. An increase in field effect mobility was observed for different OFETs with increasing grain size in C60 films. The temperature dependence of charge carrier mobility in these devices followed the empirical relation named as Meyer-Neldel Rule and showed different activation energies for films with different degree of disorder. A shift in characteristic Meyer-Neldel energy was observed with changing C60 morphology which can be considered as an energetic disorder parameter.

The mechanism of formation of hemozoin, a detoxification by-product of several blood-feeding organisms including malaria parasites, has been a subject of debate; however, recent studies suggest that neutral lipids may serve as a catalyst. In this study, a model system consisting of an emulsion of synthetic lipid bodies, resembling their in vivo counterpart in composition and size, was employed to investigate the formation of β-hematin, synthetic hemozoin, at the lipid-water interface. The introduction of heme (Fe(III)PPIX) to this synthetic neutral lipid bodies system under biomimetic conditions (37°C, pH 4.8) produced beta-hematin with apparent first order kinetics and an average half life of 0.5 min. TEM of monoglycerides (MPG) extruded through a 200 nm filter with heme produced beta-hematin crystals aligned and parallel to the lipid/water interface. TEM data suggests that beta-hematin crystallizes via epitaxial nucleation at the lipid-water interface through interaction of Fe(III)PPIX with the polar head group and elongation occurs parallel this interface.

A layer of silver nanoparticles created by thermal annealing of evaporated silver films can increase the photocurrents in silicon-on-insulator (SOI) devices by fivefold or more, but significant enhancements have been restricted to wavelengths greater than 800 nm. Here we report a significant enhancement of photoconductance at shorter wavelengths (500-750 nm) by using a monolayer of silver nanoparticles transferred from a colloidal suspension. Photocurrents on SOI increased in the 500-750 nm spectral range with the addition of silver nanoparticles, with enhancements more than two times; enhancements at longer wavelengths were small, in contrast to results with annealed silver films. We prepared similar colloidal silver nanoparticle monolayers layers on nanocrystalline silicon solar cells with conducting oxide top layers. There is an overall decrease in the quantum efficiency of these cells with the deposition of silver nanoparticles. We attribute these effects to the substantial substrate-mediated changes in the localized surface plasmon resonance frequencies of the differing nanoparticle configurations.

Thermoluminescence (TL) of La2O3 is reported for the first time. Novel La2O3 phosphor was obtained by solution combustion synthesis (SCS) in which a redox combustion process between lanthanum nitrate and urea at 500 °C is accomplished. The powder samples obtained were annealed at 900 °C during 2 h in air. X-Ray Diffraction (XRD) results showed the hexagonal phase of La2O3 for annealed powder samples. The TL glow curve obtained after exposure to beta radiation of these samples, displayed two maxima located at ˜ 101 °C and ˜ 200 °C, and a shoulder at ˜ 247 °C. Results from experiments such as dose response and fading showed that annealed La2O3 powder obtained by SCS is a promising material for radiation dosimetry applications.

A yield problem is observed with tungsten vias formed on copper interconnects. Copper migration can occur during chemical vapor deposition (CVD) of tungsten, if there are defects in the liner inside the via. Copper can react quickly with SiH4 during the early stages of tungsten deposition, when SiH4-reduction of WF6 is used. Under severe conditions, large amounts of copper diffuse out of the underlying metal layer, resulting in copper silicide formation in the via and leaving voids in the copper wire. Copper migration can be minimized by reducing the time that the wafers are exposed to SiH4.

Ni (10%) and Ni-Cu (50 and 25%, respectively) catalysts supported on alumina, magnesia and magnesium aluminate were synthesized. The characterization was carried out by X-ray diffraction, nitrogen physisorption, temperature programmed-reduction, Raman spectroscopy and SEM. The catalysts were tested in the methane decomposition reaction using a tubular fixed bed reactor operated in the range of 500-580°C under atmospheric pressure. A higher activity was observed with the bimetallic catalysts supported on alumina and magnesium aluminate. These results were explained in terms of Ni-Cu alloy formation and weak metal-support interaction. In the case of monometallic catalysts, a strong metal-support interaction was detected, which revealed the lowest activity and stability compared with the bimetallic catalysts. The formed carbon was a combination of amorphous and graphite.

Plates of Al 6063-T6 (6.35mm thick) were welded using an ER-5356 filler wire. The aim of the experiments was to assess the effects that yield the induction of an axial magnetic field (AMF) during gas metal arc (GMA) welding on the grain structure of the weld metal and on the mechanical properties of the welded joint. Magnetic fields between 0 to 15mT were induced by using a coil which was fed with different current intensities by an external power source. Plots of the grain size distribution showed that applying low magnetic fields homogenizes the grain structure of the weld metal and suppresses the typical columnar-dendritic growth from partially melted grains at the fusion line. The mechanisms involved in these phenomena are discussed with the aid of finite element analysis. Transverse microhardness profiles of the welds revealed a reduction in the loss of hardening in the heat affected zone (HAZ). The loss of hardening after fusion welding in heat treatable aluminum alloys is known as overaging and it is the result of coarsening and transformation of the strengthening phase [1]. It is thought that an electromagnetic interaction between the external magnetic field applied and the inherent magnetic field generated by the direct current of the welding process alters the diffusion process delaying over aging kinetics in the HAZ.

The hydrogenated amorphous silicon (a-Si:H) thin film transistors (TFTs) having a very high field-effect mobility of 1.76 cm2/V-s and a low threshold voltage of 2.43 V have been fabricated successfully using the hot wire chemical vapor deposition (HWCVD).

We demonstrate high performance zinc-tin oxide (ZTO) thin-film transistors (TFTs) with low operation voltage, small channel length and low parasitic capacitance. Both the zinc tin oxide and the high-k dielectric, ZrO2, were solution processed by sol-gel methods. A self-aligned process was employed to minimize the parasitic capacitance. The transistors with a channel length of 8 μm operate at 5 V and have a saturation mobility of 2.5 cm2/V·s and an on/off ratio of 5.9×106. Gate-induced surface relief has been found to have strong effect on the performance of the active layer.