ZnO/ITO core/shell nanostructure electrodes for future prototype solar cell devices

The impact of indium tin oxide (ITO) layers over vertically aligned zinc oxide nanorods (ZnO NRs) has been investigated to consider ITO nanolayers as transparent conducting oxide electrodes (TCOE) for hierarchical heteronanostructure solar cell devices that have ZnO nanostructures as branches. ZnO/ITO core/shell nanostructures were prepared in two- steps using vapor-liquid-solid and evaporation processes, and further the structures were annealed at various temperatures. Transmission electron microscopic studies show that the as-grown ZnO/ITO structures consist of an amorphous ITO shell on single crystalline ZnO cores, whereas the structures annealed above 300 degrees C consist of a single crystalline ITO shell. ITO layer deposited ZnO NRs exhibit a small red-shift in ZnO near-band-edge emission as well as optical band gap. The electrical measurements carried out on single ZnO/ITO core/shell NR under dark and UV light showed excellent thermionic transport properties. From these investigations it is emphasized that ITO nanolayers could be used as TCO electrodes for prototype ZnO based hierarchical solar cell devices.

Effects of growth temperature on nonpolar a-plane InN grown by molecular beam epitaxy

Nonpolar a-plane InN films were grown on r-plane sapphire substrate by plasma assisted molecular beam epitaxy with GaN underlayer. Effect of growth temperature on structural, morphological, and optical properties has been studied. The growth of nonpolar a-plane (1 1 -2 0) orientation was confirmed by high resolution X-ray diffraction study. The film grown at 500 degrees C shows better crystallinity with the rocking curve FWHM 0.67 degrees and 0.85 degrees along 0 0 0 1] and 1 - 1 0 0] directions, respectively. Scanning electron micrograph shows formation of Indium droplets at higher growth temperature. Room temperature absorption spectra show growth temperature dependent band gap variation from 0.74-0.81 eV, consistent with the expected Burstein-Moss effect. The rectifying behaviour of the I-V curve indicates the existence of Schottky barrier at the InN and GaN interface. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Observation of Room Temperature Ferromagnetism in InN Nanostructures

The room temperature ferromagnetic behavior of InN nanosfructures grown by molecular beam epitaxy (MBE) is explored by means of magnetization measurements. The saturation magnetization and remanent magnetization are found to be strongly dependent on the size of the nanostructures. This suggests that the ferromagnetism is essentially confined to the surface of the nanostructures due to the possible defects. Raman spectroscopy shows the existence of indium vacancies which could be the source of ferromagnetic ordering in InN nanostructures.

Growth and electrical transport properties of InGaN/GaN heterostructures grown by PAMBE

InGaN epitaxial films were grown on GaN template by plasma-assisted molecular beam epitaxy. The composition of indium incorporation in single phase InGaN film was found to be 23%. The band gap energy of single phase InGaN was found to be similar to 2.48 eV: The current-voltage (I-V) characteristic of InGaN/GaN heterojunction was found to be rectifying behavior which shows the presence of Schottky barrier at the interface. Log-log plot of the I-V characteristics under forward bias indicates the current conduction mechanism is dominated by space charge limited current mechanism at higher applied voltage, which is usually caused due to the presence of trapping centers. The room temperature barrier height and the ideality factor of the Schottky junction were found to 0.76 eV and 4.9 respectively. The non-ideality of the Schottky junction may be due to the presence of high pit density and dislocation density in InGaN film. (C) 2014 Elsevier Ltd. All rights reserved.

Optically transparent polymer devices for in situ assessment of cell electroporation

In order to study cell electroporation in situ, polymer devices have been fabricated from poly-dimethyl siloxane with transparent indium tin oxide parallel plate electrodes in horizontal geometry. This geometry with cells located on a single focal plane at the interface of the bottom electrode allows a longer observation time in both transmitted bright-field and reflected fluorescence microscopy modes. Using propidium iodide (PI) as a marker dye, the number of electroporated cells in a typical culture volume of 10-100 mu l was quantified in situ as a function of applied voltage from 10 to 90 V in a series of 2-ms pulses across 0.5-mm electrode spacing. The electric field at the interface and device current was calculated using a model that takes into account bulk screening of the transient pulse. The voltage dependence of the number of electroporated cells could be explained using a stochastic model for the electroporation kinetics, and the free energy for pore formation was found to be kT at room temperature. With this device, the optimum electroporation conditions can be quickly determined by monitoring the uptake of PI marker dye in situ under the application of millisecond voltage pulses. The electroporation efficiency was also quantified using an ex situ fluorescence-assisted cell sorter, and the morphology of cultured cells was evaluated after the pulsing experiment. Importantly, the efficacy of the developed device was tested independently using two cell lines (C2C12 mouse myoblast cells and yeast cells) as well as in three different electroporation buffers (phosphate buffer saline, electroporation buffer and 10 % glycerol).

Effect of Micro-Structured Copper as Cathode Material for P3HT-Based Diode

Here, the effect of micro-structured cathode material on the device performance of indium tin oxide/poly(3hexylethiophene)/copper diode (ITO/P3HT/Cu) is investigated. Two different forms of copper namely bulk metal (Cu{B}) and nanoparticle (Cu{N}) were used as top electrode to probe its effect on device performance. Crystallographic structure and nanoscale morphology of top Cu electrodes were characterized using X-ray diffraction and scanning electronmicroscopy. Electrode formed by evaporation of copper nanoparticle showed enhancement in current density. From capacitance based spectroscopy we observed that density of trap states in ITO/P3HT/copper larger size grain (Cu-LG) are one order greater than that in ITO/P3HT/copper smaller size grain (Cu-SG) device.

In-doped multifilled n-type skutterudites with ZT=1.8

In this paper we maximize the thermoelectric (TE) figure of merit, ZT, of n-type skutterudites, (In,Sr,Ba,Yb)(y)Co4Sb12, via three different routes: (i) find the optimum fraction of In as fourth filler (ii) check the influence of powder particle, grain, and crystallite size on the TE properties and (iii) check thermal stability. Filled n-type (Sr, Ba, Yb)(y)Co4Sb12 was mixed in three different proportions with In0.4Co4Sb12, ball milled (regular or high-energy (HB) ball milling) and hot-pressed. Particle size analyses and SEM pictures of the broken surfaces of the hot pressed samples document that only HB produces uniform particles/grains with average crystallite sizes similar to 100 nm, proven by transmission electron microscopy. X-ray Rietveld refinements combined with EDX indicate that in all cases indium entered the icosahedral voids of the skutterudite. Temperature dependent physical properties of all three regularly ball-milled samples show that increasing In-content infers an increasing electrical resistivity, increasing Seebeck coefficient but a decreasing total thermal conductivity. Although ZT (823 K) is in the same range as for the sample without In, the ZT values in the whole temperature range are higher and consequently the TE-conversion efficiency, eta is at least 10% higher. Annealing the samples at 600 degrees C for three days shows minor changes in structure and thermoelectric properties, indicating TE stability. The HB sample, due to uniformly small particles, equally sized grains and crystallites, exhibits a high power factor (4.4 mW/m K-2 at 730 K) and a very low thermal conductivity leading to an outstanding high ZT = 1.8 at 823 K (eta(max) = 17.5%). (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

NANOLOCALIZED SINGLE CELL MEMBRANE NANOELECTROPORATION

Today single cell research is a great interest to analyze cell to cell or cell to environment behavior with their intracellular compounds, where bulk measurement can provide average value. To deliver biomolecules precise and localized way into single living cell with high transfection rate and high cell viability is a challenging and promisible task for biological and therapeutic research. In this report, we present a nano-localized single cell nano-electroporation technique, where electroporation take place in a very precise and localized area on a single cell membrane to achieve high efficient delivery with high cell viability. We fabricated 60nm gap with 40 nm triangular Indium Tin Oxide (ITO) based nano-eletcrode tip, which can intense electric field in a nano-localized area of a single cell to permeabilize cell membrane and deliver exogenous biomolecules from outside to inside of the cell. This device successfully deliver dyes, proteins into single cell with high cell viability (98%). The process not only control precise delivery mechanism into single cell with membrane reversibility, but also it can provide special, temporal and qualitative dosage control, which might be beneficial for therapeutic and biological cell studies.

Sulfurization of sputtered Ag-In precursors for AgInS2 solar cell absorber layers

Silver indium sulfide (AgInS2) thin films are deposited by sequential sputtering of metallic precursor Ag/In] followed by sulfurization. Effect of substrate temperature (Tsub) during sulfurization process on the film growth is studied by varying the substrate temperature from 350 to 500 degrees C. Films prepared above 350 degrees C showed a mixture of orthorhombic and tetragonal phases of AgInS2 with tetragonal phase being dominant. Better crystalline, nearly stoichiometric and p-type films are obtained at a substrate temperature of 500 degrees C. The characteristic A(1) mode of AgInS2 chalcopyrite structure is observed in the Raman spectra at 274 cm(-1) for the films prepared above 350 degrees C. The grain size of the film increases from 489 to 895 nm with the increase in substrate temperature. The binding energies of the constituent elements are determined using XPS. The band gap of AgInS2 films is in the range of 1.64-1.92 eV and the absorption coefficient is found to be >10(4) cm(-1). Preliminary studies on the AgInS2/ZnS solar cell showed an efficiency of 0.3%. (C) 2015 Elsevier B.V. All rights reserved.

Effect Of High Pressure On The Electrical Resistivity Of Ge-Te In Glasses

The variation in the electrical resistivity of the chalcogenide glasses Ge15Te85-x has been studied as a function of high pressure for pressures up to 8.5GPa. All the samples studied undergo a semi-conductor to metallic transition in a continuous manner at pressures between 1.5-2.5GPa. The transition pressure at which the samples turn metallic increases with increase in percentage of Indium. This increase is a direct consequence of the increase in network rigidity with the addition of Indium. At a constant pressure of 0.5GPa, the normalized resistivity shows some signature of the existence of the intermediate phase. Samples recovered after a pressure cycle remain amorphous suggesting that the semi-conductor to metallic transition arises from a reduction of the band gap due to pressure or the movement of the Fermi level into the conduction or valence band.

Evaporation-Condensation Synthesis and Optical Property of In(2)O(3)Octahedrons

Synthesis of In2O3 octahedrons is carried out successfully by heating Indium metal pieces in air ambient. The sample is characterized by scanning electron microscopy (SEM), Energy dispersive X-ray spectroscope (EDS), X-ray diffraction (XRD) and Raman spectroscopy. The as-prepared In2O3 octahedrons are highly crystalline and exhibit body centered cubic structure. Room temperature and temperature (293-453K) dependence photoluminescence reveals a deep levelbroad emission of yellowish-orange spectra centered around 605 nm. The emission is due to the presence of defect levels in the band gap of materials.

Electrically conducting palladium selenide (Pd4Se, Pd17Se15, Pd7Se4) phases: synthesis and activity towards hydrogen evolution reaction

Electrically conducting, continuous films of different phases of palladium selenides are synthesized by the thermolysis of single source molecular precursors. The films are found to be adherent on flat substrates such as glass, indium tin oxide and glassy carbon and are stable under electrochemical conditions. They are electrocatalytically active and in particular, for hydrogen evolution reaction. Catalytic activities with low Tafel slopes of 50-60 mV per decade are observed.

Instability in an amorphous In-Ga-Zn-O field effect transistor upon water exposure

The instability of an amorphous indium-gallium-zinc oxide (IGZO) field effect transistor is investigated upon water treatment. Electrical characteristics are measured before, immediately after and a few days after water treatment in ambient as well as in vacuum conditions. It is observed that after a few days of water exposure an IGZO field effect transistor (FET) shows relatively more stable behaviour as compared to before exposure. Transfer characteristics are found to shift negatively after immediate water exposure and in vacuum. More interestingly, after water exposure the off current is found to decrease by 1-2 orders of magnitude and remains stable even after 15 d of water exposure in ambient as well as in vacuum, whereas the on current more or less remains the same. An x-ray photoelectron spectroscopic study is carried out to investigate the qualitative and quantitative analysis of IGZO upon water exposure. The changes in the FET parameters are evaluated and attributed to the formation of excess oxygen vacancies and changes in the electronic structure of the IGZO bulk channel and at the IGZO/SiO2 interface, which can further lead to the formation of subgap states. An attempt is made to distinguish which parameters of the FET are affected by the changes in the electronic structure of the IGZO bulk channel and at the IGZO/SiO2 interface separately.

InN Quantum Dot Based Infra-Red Photodetectors

Self-assembled InN quantum dots (QDs) were grown on Si(111) substrate using plasma assisted molecular beam epitaxy (PA-MBE). Single-crystalline wurtzite structure of InN QDs was confirmed by X-ray diffraction. The dot densities were varied by varying the indium flux. Variation of dot density was confirmed by FESEM images. Interdigitated electrodes were fabricated using standard lithography steps to form metal-semiconductor-metal (MSM) photodetector devices. The devices show strong infrared response. It was found that the samples with higher density of InN QDs showed lower dark current and higher photo current. An explanation was provided for the observations and the experimental results were validated using Silvaco Atlas device simulator.

A Deep-Blue Electroluminescent Device Based on a Coumarin Derivative

The design and synthesis is reported of 7-(9H-carbazol-9-yl)-4-methylcoumarin (Cz-Cm), comprising a carbazole donor moiety and a 4-methylcoumarin acceptor unit, for use in a blue organic light-emitting diode. A detailed solid state, theoretical and spectroscopic study was performed to understand the structure-property relationships. The material exhibits deep-blue emission and high photoluminescence quantum yield both in solution and in a doped matrix. A deep-blue electroluminescence emission at 430nm, a maximum brightness of 292cdm(-2) and an external quantum efficiency of 0.4% was achieved with a device configured as follows: ITO/NPD (30nm)/TCTA (20nm)/CzSi(10nm)/10wt% Cz-Cm:DPEPO (10nm)/TPBI (30nm)/LiF (1nm)/Al ITO=indium tin oxide, NPD=N,N-di(1-naphthyl)-N,N-diphenyl-(1,1-biphenyl)-4,4-diamine, TCTA=tris(4-carbazoyl-9-ylphenyl)amine, CzSi=9-(4-tert-butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole, DPEPO=bis2-(diphenylphosphino)phenyl]ether oxide, TPBI=1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene].