The inner composition, defect content and morphology of AlGaAs nanowires (NWs) grown on (111)B-GaAs by Au-catalyzed MOVPE is reported. The NWs grow tapered with their [111] axis normal to the substrate. The Raman spectra of single AlGaAs NWs were measured in non-resonant conditions with sub-μ-meter spatial resolution, allowing determination of the Al content. NWs consist of GaAs for TG<475°C, but show a two-fold compositional structure for TG >475°C, namely an AlxGa1-xAs core surrounded by an AlyGa1-yAs (y<x) shell, ascribed to the combination of Au-catalyzed (axial) and conventional (sidewall) growth. The cross-sectional shape of AlGaAs NWs changes from triangular (for TG=500÷525°C) to almost hexagonal (for TG=550°C), due to an exchange between and {110} planes as the slowest to grow. The NWs have free-electron concentrations ∼1018 cm-3, due to Si contamination of the Al source.

Organic materials or polymers, which are widely used in electronic devices, are easily damaged by energetic ion or electron bombardment. Therefore, it is difficult to use conventional ion or electron beam processes for etching organic materials. In this study, a gas cluster beam possessing kinetic energy of the order of several hundred eV was used as a novel means to realize high-rate, low-damage etching. Polyethylene (PE) and polyvinyl chloride (PVC) were used as the target organic materials. Using a SF6 cluster beam, the etching depth suddenly increased when the nozzle gas pressure exceeded 0.6 MPa, as in the case of cluster beam formation. When the SF6 gas pressure in the nozzle was 1.2 MPa, the etching rates of PVC and PE were 2.88 μm/s and 1.62 μm/s, respectively. The dependence of the etching effect on cluster size was studied by varying the gas temperature. The etching depth of PVC increased with increasing average cluster size and intensity of the beam. The flow rate of the gas was constant; hence, etching of the organic materials did not occur because of the individual impact of the molecular beam. In fact, it occurred because of the neutral cluster, which had a large total kinetic energy. The energy per molecule of the gas cluster beam is of the order of several tens of meV; hence, high-rate, low-damage etching of organic materials can be potentially achieved.

We demonstrate improved compatibility of poly(ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) hole transport layer with acid-sensitive materials by addition of a simple base, NaOH or NH4OH, to the aqueous suspension to increase pH. Addition of NaOH to the acidic PEDOT:PSS allowed the deposition of PEDOT:PSS on top of an inverted poly(3-hexylthiophene):ZnO nanoparticle blend hybrid photovoltaic device, and improved device performance due to preservation of the ZnO electron acceptor. To quantitatively investigate the impact of base addition to hole transport layer properties and device performance, we deposited PEDOT:PSS with different pH values on inverted poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester bulk heterojunction devices. We find that NaOH modification results in a substantial work function decrease and series resistance increase. In contrast, the volatile NH4OH leaves PEDOT:PSS with minimal changes in film properties and device performance.

Printed electronics is a seminal technology for the production of simple disposable electronic products. In comparison to conventional silicon electronics it offers the possibility to use potentially cheap materials (e.g. polymers) which can be processed as solutions or dispersions by means of highly productive mass printing technologies. One main aim is the production of fully mass printed electronic circuits for the identification of single items, which should not cost more than one cent per tag. For the realization several challenges have to be clarified. On the one hand the performance of the - often organic - materials has to be increased in interaction with the used printing technologies. On the other hand the printing methods themselves have to be adapted and continuously improved. Alternatively, new approaches for the preparation of structured thin films have to be developed. This paper introduces a new technique for the production of source/drain electrodes with high resolution.

Zinc oxide layers with a thickness of less than 10 nanometers have been synthesized from an aqueous solution for the application as active layer in thin film transistors. They have been conditioned by applying different oxidizing and reducing atmospheres during an annealing process at a temperature of 125°C. It is shown that the charge carrier mobility and threshold voltage is strongly influenced by the annealing atmosphere. Samples annealed in 10% forming gas (H2 in N2 - reducing atmosphere) show the highest field-effect-mobility of 0.6 cm2V-1s-1, but no saturation of the drain current, due to a high free carrier concentration. Samples treated under oxygen (strongest oxidizing atmosphere) show significantly lower mobilities. Subsequently, the samples have been exposed to synthetic air, with varying exposure times. Samples which have been annealed under hydrogen atmospheres show a pronounced decay of the drain current if exposed to synthetic air, whereas all samples conditioned under hydrogen-free atmospheres are significantly more stable under synthetic air. This enhanced sensitivity against oxygen after hydrogen treatment is attributed to residual hydrogen content in the sample that supports the formation of OH-groups which act as electron acceptors.

The model of single vortex escape from extended linear defect and subsequent vortex dynamics under the Lorentz force action in a rather thick (d > 2λ) 3D anisotropic superconductor is developed. We consider the case of parallel c-oriented linear defects as well as the case of equidistant linear row of such kind of defects, which represents the dislocation model of low-angle [001] tilt grain boundary in HTS films and bicrystals. The suggested model based on the classical mechanics approach allows to describe behavior of an elastic vortex string in the potential well of linear defect and under the action of Lorentz force on its end within the Meissner current carrying layer and to determine the depinning critical current density at low magnetic fields and temperatures.

Despite the availability of many high-volume and low-cost manufacturing processes for LED-based lighting applications, relying mainly on fixed patterns such as LED-backlights and RGB-pixelated displays, novel applications, such as “mood lighting” or interior wall displays call for more complicated and shaped LED arrangements. The presented work is based of a novel roll-to-roll (R2R) process to adaptively and cost-efficiently generate LED arrangements on RMPD® substrates.

Inkjet printing of planar and though-hole electrical interconnections is of high importance to the process, as it provides a fully digital way of interconnecting devices electrically, accounting for the actual position of the component and spatially provide different ink film thicknesses.

Xaar’s industrial inkjet printheads are used to dispense defined volumes of 50 pL of a silver nanoparticle ink in order to provide high reliability and good positioning accuracy while main-taining low satellite drop densities. Specific printing strategies are investigated at a print speed of 0.1 m/s to allow for a reliable electrical connection in case of up to 50 μm deep via connections to the buried component.

Due to the low glass-transition nature of the underlying substrates, low sintering tempera-tures are required to preserve the mechanical properties of the substrate. Low temperature oven sintering yielding sufficient conductivity to drive a current of 40 mA will be discussed.

In this work, thin films of Indium Tin Oxide (ITO)-based materials were tested as potential candidates for mid-IR transparent contacts on Te-doped GaSb and Si-doped InAs semiconductor wafers. Since these contacts are devoted to be inserted in Sb-based devices which are generally MBE-grown at ∼450°C, low-temperature fabrication processes were particularly tested with a maximum temperature of annealing of 400°C. 50 nm-thick ITO films were deposited on glass, Te-doped GaSb and Si-doped InAs wafers and resistivity of 8.10−4 Ω.cm combined with ∼80% of transmittance at 2 μm and ohmic contacts with a specific resistance of 3.10−4 Ω.cm2 were obtained. Then, in order to improve these properties in the mid-IR, other ITO-based materials were tested: In doped ZnO (IZO) and Zn doped ITO (ITZO). The first results obtained on these materials show that the insertion of 10% of Zn in classical ITO structure results in a degradation of the electrical properties of the layer without a real impact on its optical transmittance near 2 μm. Concerning IZO, a large improvement of the transmittance in the whole visible-mid-IR wavelength range was observed for annealed samples at a temperature as low as 350°C. However, the electrical resistivity appears very sensible to the temperature of annealing.

In this paper, we introduce a novel reconfigurable graphene logic based on graphene p-n junctions. In this logic device, switching is accomplished by using co-planar split gates that modulate the properties that are unique to graphene, including ambipolar conduction, electrostatic doping, and angular dependent carrier reflection. In addition, the use of these control gates can dynamically change the operation of the device, leading to reconfigurable multi-functional logic. A device model is derived from carrier transmission probability across the p-n junction for allowing quantitative comparison to CMOS logic. Based on this model, we show that the proposed graphene logic has significant advantages over CMOS gate in terms of area, delay, power, and signal restoration. Furthermore, the device utilizes a large graphene sheet with minimal patterning, allowing feasible integration with CMOS circuits, for potential CMOS-graphene hybrid circuits.

The thermal conductivity of amorphous indium zinc oxide (IZO) thin films was measured by the 3ω method. Three IZO films were prepared by dc magnetron sputtering method on Si substrate under different O2 flow ratios (O2 / [Ar+O2]) of 0%, 1%, and 5%. The thermal conductivity of IZO films decreases with an increase in O2 flow ratio, the values of the thermal conductivity were 3.4, 3.1 and 1.2 W m-1 K-1 for O2 flow ratios of 0%, 1%, and 5%, respectively. To investigate relationships among the thermal conductivity, the structure and other physical properties, we were carried out nanoindentation, Rutherford back scattering (RBS), electron spin resonance (ESR). The result of ESR measurements indicated that the amount of conduction electron in the IZO film decreases with increasing O2 flow ratio. Increase of O2 flow ratio reduces the amount of oxygen vacancies for providing free electrons. Therefore, decreasing thermal conductivity with an increase in O2 flow ratio is attributed to decreasing conduction electrons as thermal carrier. On the other hand, the chemical composition of IZO films is independent of O2 flow ratio. Furthermore, density, Young’s modulus and hardness also show little changes with increasing O2 flow ratio. Density, Young’s modulus and hardness are strongly associated with the internal structure. It is probable that influence of oxygen vacancies on the internal structure of IZO film is negligibly small.

Thin lithium layers on oxygenated C(100) boron-doped diamond have been observed using x-ray photoemission spectroscopy. Conductive boron-doped diamond was oxygen-terminated using an ozone cleaner. Lithium was evaporated onto the oxygen-terminated C(100) surface and an as-grown hydrogen terminated surface to a thickness of approximately 50 nm. After washing with deionised water, significant lithium signal is still detected on oxygenated diamond, but not on hydrogenated diamond, indicating a strongly bound lithium-oxygen surface layer is formed, as predicted by recent theoretical modeling.

The development of materials with high stability and high charge mobility is urgent for commercial application of blue phosphorescent organic light emitting devices (PHOLED). Silicon based inorganic-organic hybrid materials with ultra high glass transition temperature (over 150 °C) and high charge mobility (over 1.16 x 10-3 at 5 x 105 V/cm) were synthesized. These showed high external quantum efficiency of over 19%, and deep blue color coordinates of (0.15, 0.23), when they were used as a host materials in the PHOLED.

The origin of the above interesting properties was investigated by experimental measurements complemented by DFT calculations. Estimations of the structure-property relationship of a molecule in an amorphous thin film would be presented

Polyacrylamide- Multiwalled carbonnanotube (PAM- MWNT) composites were prepared via free radical crosslinking copolymerization with different amounts of MWNT varying in the range between 0.1 and 15 wt. %. PAM- MWNT composite gels were characterized by fluorescence, dielectric spectroscopy and the tensile testing technique. A small content of doped nanotubes dramatically changed gelation time, conductivity and young modulus, respectively. The gel fraction exponent, β of PAM- MWNT composite gels were measured for various monomer and MWNT concentrations and observed that the gel fraction exponent β agrees best with the percolation theory for various amounts of PAM- MWNT. These polymer systems which are initially of an isolator character are doped with carbon nanotubes of nano dimensions and when the amount of this addition exceeds a critical value (0.3 wt. % MWNT) known as the percolation threshold, then composite gel systems with carbon nanotubes become electrically conducting structures with a critical exponent around r=2 which is close to the theoretical prediction of this value in 3D percolated system as known random resistor network. The observed elasticities are decreased above 3 wt. %MWNT with critical exponent around y=0.72 which is indicative of a transition from liquid-like to solid-like viscoelastic behavior.

Multi-component small molecule systems that are amphiphilic or that can hydrogen bond end-to-end or side-to-side have been shown to self-assemble into a variety of shapes including fibers, rods, sheets, plates, spheres, and tubes. Recently, we have identified a simple route to self-assemble the same shapes from one-component systems. The structures form by attaching ethyl vinyl sulfone (EVS) to amino acids in water at room temperature. Choice of amino acid, amount of EVS substitution, and solvent conditions determine the final shape. Functionalized amino acids spontaneously form structures like fibers, spheres, tubes, and donuts when dried from solution. Here we focus on fibers and tubes.

Wire shading during thin film deposition is a promising approach to low-cost, high volume manufacturing of flexible thin film photovoltaic modules. This contribution demonstrates successful patterning of a transparent conducting oxide layer by wire shading during dynamic web coating. Continuous sputter deposition of Al-doped ZnO on a 30 cm wide polymer foil and simultaneous wire shading form 1 cm wide and 300 cm long front contact stripes for thin film photovoltaic modules. Analysing the distribution of lateral shunt resistances after separating the initial 28 stripes into 1323 pieces, yields a patterning success of 97.3 %. Thus the technique seems well suited for flexible modules from organic solar cells.

Hydrogen terminated diamond field effect transistors (FET) of 50nm gate length have been fabricated, their DC operation characterised and their physical and chemical structure inspected by Transmission Electron Microscopy (TEM) and Electron Energy Loss Spectroscopy (EELS). DC characterisation of devices demonstrated pinch-off of the source-drain current can be maintained by the 50nm gate under low bias conditions. At larger bias, off-state output conductance increases, demonstrating most likely the onset of short-channel effects at this reduced gate length.

Experimental results are presented to demonstrate feasibility of small scale power generation using static reverse electrodialysis (RED) of CuSO4 solutions. In contrast to conventional macro scale reverse electrodialysis, the concentrated and diluate compartments were not refreshed, resulting in limited power delivery times. This is important in energy harvesting applications from limited supply of ionic concentrations. Maximum output power density of 0.17 μW·cm−2 was recorded using microfiltration membranes. The evolution of the open circuit output voltage with time is accurately modeled at various concentration ratios.

Zinc oxide is a wide band gap material with excellent semiconducting, photonic and piezoelectric properties. In the past ten years zinc oxide nano-structures such as nanowires and nanorods have received great interest due to their unique dimensional and material properties in the area of photonics, electronics, mechanics, energy recovery, etc. In this paper we report the manufacturing process of a new shape, i.e. hollow hexagonal ZnO nano-cones. We grew them on different kinds of substrate using a low pressure, catalyst free, metal organic chemical vapor deposition (MOCVD) process on a FirstNano EasyTube 3000™ MOCVD system. Nitrogen was used as carrier gas to bring the reactants, DEZ and H2O, to the substrate surface. At the right balance of process temperature and carrier/precursor gas flow rate the ZnO nano-structure transitioned into a hollow hexagonal cones growth mode. The both one and two dimensional aspects of these catalyst free hollow hexagonal ZnO nano-cones, which are novel to the best of our knowledge, could lead to new applications in photonics, near field probing, chemical sensors, quantum confinement, electronic, etc.

A transient response technique has been employed to investigate the lifetime of free polarons in bulk heterojunction blends of regioregular poly (3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61 butyric acid methylester (PCBM) at different annealing temperatures. Device efficiency and charge mobility were also measured. The longest lifetime, ∼ 1.5 microseceonds, was achieved for an annealing temperature of 140˚C; this represents a 2.5 x increase in lifetime relative to unannealed samples. The 140˚C annealing temperature also yields the highest efficiency. These measurements provide an estimate of the mobility-lifetime product, a figure of merit for charge transport in organic bulk heterojunctions.