bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optical bias controlled amplification in tandem Si-C pinpin devices
Authors: Vieira M. , Vieira M. A , Louro P. , Fernandes M. , Fantoni A. , Barata M. 
Published: September 2011

ABSTRACTA monolithic double pi’n/pin a-SiC:H device that combines the demultiplexing operation with the simultaneous photodetection and self amplification of the signal is analyzed under different electrical and optical bias conditions at low and high excitation frequencies. Results show that the transducer is a bias wavelength current-controlled device that make use of changes in the wavelength of the background to control the power delivered to the load. Self optical bias amplification or quenching under uniform irradiation and transient conditions is achieved. The device acts as an optical amplifier whose gain depends on the background wavelength and frequency. An optoelectronic model supported by an electrical simulation explains the operation of the optical system.
Self optical gain in multilayered silicon-carbon heterostructures: A capacitive active band-pass filter model
Authors: Vieira M. A. , Vieira M. , Louro P. , Fernandes M. , Costa J. , Garção A. S. 
Published: September 2011

ABSTRACTThis paper reports results on the use of a pi’n/pin a-SiC:H heterostructure as an active band-pass filter transfer function whose operation depends on the wavelength of the trigger light, on the applied voltage and on the wavelength of the additional optical bias.Results show that the device combines the demultiplexing operation with the simultaneous photodetection and self amplification of the signal. Experimental and simulated results show that the output signal has a strong nonlinear dependence on the light absorption profile. The device, modeled by a simple circuit with variable capacitors and interconnected phototransistors through a resistor, is a current-controlled device. It uses a changing capacitance to control the power delivered to the load acting as a state variable filter circuit. It combines the properties of active high-pass and low-pass filter sections into a capacitive active band-pass filter.
OPTICAL LAYERS AND MATERIALS FOR NEXT GENERATION SOLAR CELLS
Authors: Lee Ping , Shank Jason , Magsi Komal , Kang Yeona , Fortmann C.M. 
Published: September 2011

AbstractLayers that enhance light scattering and Raman-scattering-based spectral modification for solar cell applications were investigated. Titanium-oxide based rear diffuse reflector were found to increase the long wavelength response of crystalline solar cells. Also particle within the Titanium-oxide produce a far greater Stokes and anti-Stokes shift when compared to bulk crystal counterparts. The anti-Stokes to Stokes shift ratio in these particle systems is also greater and increased with increasing probe or bias light intensity. When applied to solar cells these layers extend the red response and thereby increase the overall performance.
Rapid Plasma-Assisted, Ambient-Pressure Deposition of Conformal Nanocrystalline Zinc Oxide Thin Films for Solar Cell Applications
Authors: Pedersen Joachim D. , Teh Kwok Siong 
Published: September 2011

ABSTRACTThis paper reports a plasma-assisted, rapid, ambient-pressure, low-temperature one-step process for depositing conformal, non-porous nanocrystalline ZnO thin film on various substrates ranging from Si (100), fused quartz, glass, muscovite, c- and a-plane sapphire (Al2O3), to the common polymer polyimide (KaptonTM). The as-synthesized polycrystalline films range in thickness from 20nm to 200nm, deposited at a growth rate ranging from 2 nm/min to 50 nm/min. The lowest deposition temperature achieved with this method is 180°C and progress is being made in further lowering this temperature. The as-deposited films are highly oriented in the caxis, with (002) being the dominant planes.
Pore-opening Process in Nanoporous AAO Membranes for Electrodeposition of Semiconducting Nanowires
Authors: Phok Sovannary , Rajaputra Suresh S. , Singh Vijay P. , Al-Thani Hamda A. , Hasoon Falah 
Published: September 2011

ABSTRACTThe fabrication of nanoporous aluminum oxide (Al2O3) membranes for large scale production of nanowires is performed at room temperature by a two-step anodization of commercially available aluminum foil tapes. During the anodization process, an oxide barrier layer is formed at the interface with aluminum. In the present work, the removal of the barrier is performed by (i) ramping down the voltage with a rate in the range of 0.5 V per 60s to 2 V per 60s and (ii) immersing the substrate in 50% phosphoric acid for up to 5 minutes. Depending on the removal conditions, several morphologies at the oxide-aluminum interface are observed by Scanning Electron Microscopy (SEM). Ramping down the voltage at less than 0.3 V per 15s combined by immersion in 50% phosphoric acid for less than 3 minutes is found to open the barrier layer of the nanopores. The pores have root-like structure with branches as small as few nanometers due to the slow voltage ramping. Several amorphous anodized Al2O3 (AAO) templates with pore diameter ranging from 30 to 40 nm and with length up to 25 μm were prepared by two-step anodization for the cathodic electrodeposition of photoactive nanowire semiconductors such as copper indium diselenide and cadmium sulfide.
Structural Study of CIGS2 Thin Film Absorbers using EBSD Technique
Authors: Kaul Ashwani , Pethe Shirish A. , Dhere Neelkanth G. , Moutinho Helio R. 
Published: September 2011

ABSTRACTIn this study electron backscatter diffraction (EBSD) investigation is carried out for CuIn1-xGaXS2 (CIGS2) samples that were prepared by two stage process in which the initial precursor was deposited by DC magnetron sputtering followed by sulfurization in conventional furnace. Due to high surface roughness, low quality EBSD signal was obtained in the samples that were initially polished with ion milling. Polishing with dimpler grinder followed by chemical treatment with bromine/methanol solution improved the quality of EBSD patterns. Efforts are being made to build the database for CIGS2 in the system using high quality EBSD patterns and finally to obtain grain orientation maps.
Electrospun Composite Nanofiber Transparent Conductor Layer for Solar Cells
Authors: Ritchie Justin , Mertens Joël , Yang Heejae , Servati Peyman , Ko Frank K. 
Published: September 2011

ABSTRACTDeveloping a durable and scalable transparent conductor (TC) as an electrode with high optical transmission and low sheet resistance is a significant opportunity for enabling next generation solar cell devices. High performance fibrous composite materials based on a carrier polymer with embedded functional nanostructures have the potential to serve as a TC with high surface area that can be deposited by the novel and scalable process of electrospinning. This work presents the development of a fibrous TC, where polyacrylonitrile (PAN) is used as a carrier polymer for multi-walled carbon nanotubes (MWCNT) to create electroactive nanofibers 200-500nm in diameter. Once carbonized, thin layers of this material have a low sheet resistance and high optical transmission. It is shown that in a two stage carbonization process, the second stage temperature of above 700C is the primary factor in establishing a highly conductive material and single layers of nanofibers are typically destabilized at high temperatures. A high performance TC has been developed through optimizing carbonization rates and temperatures to allow for single nanofiber layers fabricated by electrospinning MWCNT/PAN solutions onto quartz. These TCs have been optimized for concentrations of MWCNTs less than 20% volume fraction with well above 90% transmissivity and sheet resistances of between .5-1kohm/square. The required MWCNT loading is well below that for TCs based on random networks of MWCNTs.
Comparative Study on Manufacturability of Selective Emitter and Double Printing on Mono-Si PV Cells
Authors: Liu Y. , Jiang F.D. , Wang S. , Zeng Y. , Shan W. 
Published: September 2011

ABSTRACTSelective emitter structure has long been regarded as a good and relatively simple approach to improve the energy conversion efficiency of Si wafer-based single-junction photovoltaic (PV) cells. Recently emerged double printing method, on the other hand, potentially has the capability of improving the efficiency with no requirement for device structure modification. The manufacturability of these two approaches has been studied on a mass-production platform at JA Solar recently with large scale sampling. The experimental results collected from over two hundred thousand cells demonstrated that both approaches are capable of achieving significant conversion-efficiency gain in a cost-effective way with high yield rate on the PV industry commonly used mass production platform currently adopted by the vast majority of cell manufacturers
Roll-to-Roll Front Contact Patterning by Wire Shading
Authors: Merz R. , Schubert M. B. , Werner J. H. 
Published: September 2011

ABSTRACTWire 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.
Characterization of Thin Film CdTe photovoltaic materials deposited by high plasma density magnetron sputtering
Authors: Abbas A. , Bowers J.W. , Maniscalco B. , Moh S. , West G.D , Rowley P.N. , Upadhyaya H.M , Walls J. M. 
Published: September 2011

ABSTRACTA new magnetron sputtering strategy is introduced that utilizes high plasma density (~5mA.cm-2) to avoid or reduce high temperature processing. The technique uses magnetrons of opposing magnetic polarity to create a “closed field” in which the plasma density is enhanced without the need for high applied Voltages. A batch system has been used which employs a rotating vertical drum as the substrate carrier and a symmetrical array of linear magnetrons. The magnetrons are fitted with target materials for each of the thin films required in the photovoltaic (PV) stack including the CdTe absorber layer, CdS window layer, metal contact using the conventional superstrate configuration. The “closed field” sputtering technology allows scale up not only for larger batch system designs but it is also configurable for “in-line” or “roll to roll” formats for large scale production. The morphology of each of the layers is characterized using a variety of structural and optical techniques including Field Emission Gun SEM and X-ray diffraction (XRD).
Large-Scale Deposition of Transparent Conducting Oxides by Hollow Cathode Sputtering
Authors: Delahoy Alan E. , Jansen Kai , Robinson Chris , Varvar Anthony , Fabiano Paul , Kappera Rajesh , Guo Sheyu , Li Hongmei , Yang Shaohua 
Published: September 2011

ABSTRACTThis paper reviews the status of hollow cathode sputtering as an evolving technology for production of thin-film transparent conducting oxides for PV applications. A large market segment for PV TCOs is represented by thin-film a-Si:H and tandem a-Si:H/nc-Si:H modules. For superstrate devices, textured SnO2:F produced on-line by APCVD is currently the market leader, although alternative off-line methods and materials are now emerging. In particular, zinc oxide can be produced by LPCVD, APCVD, magnetron sputtering, and hollow cathode sputtering (HCS). HCS is a stable process featuring low-cost metal targets and a soft deposition process. We discuss the deposition principles and the film results obtained using linear hollow cathodes 0.5 m and 1.0 m in length. We report the direct deposition of highly textured doped ZnO having an electron mobility in excess of 50 cm2/Vs. The production cost of textured ZnO is estimated for several competing techniques.
Comparison of Aluminum Nitride Nanowire Growth with and without Catalysts via Chemical Vapor Deposition
Authors: Teker Kasif , Oxenham Joseph A. 
Published: September 2011

ABSTRACTThis paper presents a systematic investigation of AlN nanowire synthesis by chemical vapor deposition using Al and NH3 on SiO2/Si substrate and direct nitridation of mixture of Al-Al2O3 by NH3. A wide variety of catalyst materials, in both discrete nanoparticle and thin film forms, have been used (Co, Au, Ni, and Fe). The growth runs have been carried out at temperatures between 800 and 1100oC mainly under H2 as carrier gas. It was found that the most efficient catalyst in terms of nanowire formation yield was 20-nm Ni film. The AlN nanowire diameters are about 20-30 nm, about the same thickness as the Ni-film. Further studies of direct nitridation of mixture of Al-Al2O3 by NH3 have resulted in high density one-dimensional nanostructure networks at 1100oC. It was observed that catalyst-free nanostructures resulted from the direct nitridation were significantly longer than that with catalysts. The analysis of the grown nanowires has been carried out by scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and x-ray diffraction.
Dependence of the Elastic Moduli of Skutterudites on Density and Temperature
Authors: Rogl G. , Puchegger S. , Zehetbauer M. , Grytsiv A. , Rogl P. 
Published: September 2011

ABSTRACTThe dependency of Young’s and shear modulus on relative density and temperature was determined for three series of skutterudites: p-type MmyFe3CoSb12 (y = 0.70, 0.80), p-type DDyFe3CoSb12 (y = 0.65, 0.68) and n-type Sr0.07Ba0.07Yb0.07Co4Sb12. For all three groups of materials the dependency of Young’s modulus, E, on the density and temperature is linear: E(d) = 4.1(1)×d – 268(3) GPa (d is the relative density in %), ΔE/ΔT = 0.20(1) GPa/K, thus allowing extrapolation of E as a function of temperature and towards 100% density.
Thermoelectric Properties of Er-doped InGaN Alloys for High Temperature Applications
Authors: Aryal K. , Feng I. W. , Pantha B. N. , Li J. , Lin J. Y. , Jiang H. X. 
Published: September 2011

ABSTRACTThermoelectric (TE) properties of erbium-silicon co-doped InxGa1-xN alloys (InxGa1-xN: Er + Si, 0≤x≤0.14), grown by metal organic chemical vapor deposition, have been investigated. It was found that doping of InGaN alloys with Er atoms of concentration, N[Er] larger than 5x1019 cm-3, has substantially reduced the thermal conductivity, κ, in low In content InGaN alloys. It was observed that κ decreases as N[Er] increases in Si co-doped In0.10Ga0.90N alloys. A room temperature ZT value of ~0.05 was obtained in In0.14Ga0.86N: Er + Si, which is much higher than that obtained in un-doped InGaN with similar In content. Since low In content InGaN is stable at high temperatures, these Er+Si co-doped InGaN alloys could be promising TE materials for high temperature applications.
Nano-Structured Materials for Next Generation Fuel Cells and Photoelectrochemical Devices
Authors: Tuller Harry L. , Engel Johanna , Litzelman Scott J. , Bishop Sean R. 
Published: September 2011

ABSTRACTProgress in achieving improved performance in the generation and utilization of hydrogen depends on our ability to identify materials with optimized electrical and (photo)- electrochemical performance. Given their high volume fraction of interfaces, high chemical stability and versatility (ionic, electronic, optical property control), nanocrystalline electroceramic materials are of growing interest for advanced energy conversion and storage technologies. As grain size decreases towards the Debye length and grain boundaries come in closer proximity, space charge properties begin to dominate, resulting in modified charge transport. Through systematic variation of grain boundary properties by heterogeneous indiffusion of cations, the electronic and ionic carrier profiles in the space charge region may be altered. The relationships between space charge potential and defect profiles in the space charge regions are quantitatively analyzed, and implications for nano-ionic materials in thin film solid oxide fuel cells are discussed. From the standpoint of photoelectrochemical water splitting for hydrogen generation, optimizing the band gap, band alignments, and transport properties while retaining stability has remained a challenging objective. Novel nanocrystalline composite structures are discussed which exhibit features amenable to optimization of required properties and electrical measurements to determine key transport properties of titanium dioxide nanopowder, a photoanode material are introduced.
Influence of Copper on the Switching Properties of Hafnium Oxide-Based Resistive Memory
Authors: Briggs B.D. , Bishop S.M. , Leedy K.D. , Butcher B. , Moore R. L. , Novak S. W. , Cady N.C. 
Published: September 2011

ABSTRACTHafnium oxide-based resistive memory devices have been fabricated on copper bottom electrodes. The HfOx active layers in these devices were deposited by atomic layer deposition at 250 °C with tetrakis(dimethylamido)hafnium(IV) as the metal precursor and an O2 plasma as the reactant. Depth profiles of the HfOx by x-ray photoelectron spectroscopy and secondary ion mass spectroscopy revealed a copper concentration on the order of five atomic percent throughout the HfOx film. This phenomenon has not been previously reported in resistive switching literature and therefore may have gone unnoticed by other investigators. The MIM structures fabricated from the HfOx exhibited non-polar behavior, independent of the top metal electrode (Ni, Pt, Al, Au). These results are analogous to the non-polar switching behavior observed by Yang et al. [2] for intentionally Cu-doped HfOx resistive memory devices. The distinguishing characteristic of the material structure produced in this research is that the copper concentration increases to 60 % in a conducting surface copper oxide layer ~20 nm thick. Lastly, the results from both sweep- and pulse-mode current-voltage measurements are presented and preliminary work on fabricating sub-100 nm devices is summarized.
Red-emitting Ca1-xSrxS:Eu2+ Phosphors as Light Converters for Plant-growth Applications
Authors: Xia Qi , Batentschuk Miroslaw , Osvet Andres , Richter Peter , Häder Donat P. , Schneider Jürgen , Wondraczek Lothar , Winnacker Albrecht , Brabec Christoph J. 
Published: September 2011

ABSTRACTA series of Ca1-xSrxS:Eu2+y mol% phosphors were synthesized with solid state reactions and with various Ca/Sr ratio and Eu2+ doping concentrations. The influences of the lattice composition and the Eu2+ doping level on photoluminescent properties were analyzed. With doping concentrations between 0.1 to 3 mol%, concentration quenching takes place leading to the decrease of luminance; the emission maxima are also red-shifted. Further, this work reports enhanced photosynthetic activities of intact spinach leaves due to spectral modification of simulated solar irradiation by one synthesized phosphor (Ca0.4Sr0.6S:Eu1 mol%). The CO2 assimilation rates of intact spinach leaves were monitored with an effective homemade photosynthesis measurement system with controlled light conditions. The phosphor could efficiently convert the photosynthetically less active green part of the solar spectrum into the red, with a broad-band red emission centered at 650 nm and a halfband-width of 68 nm, giving an excellent match with the absorption spectrum of spinach chloroplasts. By careful referencing the photon flux, we found an enhanced photosynthetic activities by about 30 % due to the emission of the phosphor.
Single-Molecule Rapid Imaging of Linear Genomes in Nanochannel Array
Authors: Austin M. D. , Deshpande P. , Requa M. , Kunkel M. , Sadowski H. , Bozinov D. , Sibert J. , Gallagher S. , Stedman W. , Fernandes N. , Thomas A. , Das S. , Hastie A. , Finklestein J. , Marlin A. , Xiao M. , Cao H. 
Published: September 2011

ABSTRACTHuman genomic structural variation (SV) is significant factor in genome complexity, and thus has substantial implications to the cause, development and progression of genetic diseases. These SVs, ranging in size of 1kbp-1Mbp, are challenging to assess with current technologies. As such, we have developed a commercial system (nanoAnalyzer® 1000) for the rapid linear analysis of genomes at single-molecule level.The core of our system is a nanofluidic chip consisting of an array of channels with a diameter less than 100 nm, nanofabricated on the surface of a silicon substrate. Thousands of unamplified genomic DNA molecules of 100’s kbps to several Mbps can be isolated and linearly streamed into the array for analysis in a parallel fashion. Fluorescently labeled sequence-specific signatures can then be identified and aligned to reference patterns at high resolution with custom software. This automated, multi-color imaging platform will enable a wide range of applications, such as accurate sequencing assembly, discovering genome structural variations, and uncovering epigenomic content. Nanochannel arrays promise to substantially lower the barriers of entry for single-molecule DNA analysis for scientists and clinicians, greatly impacting the advancement of molecular diagnostics, personalized medicine, and biomedical research.
The Invariance of Electrowetting Contact Angle Saturation to Polymer, Fluid, and Interfacial Materials Properties
Authors: Chevalliot Stéphanie , Heikenfeld Jason 
Published: September 2011

ABSTRACTThe electrowetting equation predicts contact angle modulation to zero degrees as voltage is continually increased. However, in practice contact angle appears to saturate around 60 to 70°. Although several hypotheses have been advanced to explain the physical mechanisms of contact angle saturation, none satisfactorily and unequivocally holds for the large body of electrowetting data. Herein we experimentally demonstrate that under DC voltage electrowetting contact angle saturation is invariant to polymer, fluid, and interfacial materials properties. We furthermore reveal that saturation is also a time-dependant phenomenon.
Single-Carrier Devices for the Understanding of the Voltage Drift in Organic Light Emitting Diodes
Authors: Boizot J. , Gohri V. , Doyeux H. 
Published: September 2011

ABSTRACTThe aim of this study is to analyze and mitigate the voltage drift phenomenon observed in top-emitting organic light emitting diodes (OLED) when driven at constant current. An operating device may experience voltage increase over time due to factors such as interface or bulk material degradation, charge accumulation and formation of trap states. Single-carrier devices were fabricated to understand the contribution to voltage drift from each of these causes. Doping in electron injection layer (4, 7-diphenyl-1,10-phenanthroline or Bphen) and hole injection layer (2,2’,7,7’-tetra(N,N-di-tolyl)amino-spiro-bifluorene or Spiro-TTB) were optimized to obtain ohmic injection contacts. Devices with tris(8-hydroxy-quinoline) aluminium (Alq3) degrade significantly with holes injection and undergo high voltage increase in lifetime test measurements. On the contrary, devices with N,N’-di(naphtalen-1-y1)-N,N’-diphenyl-benzidine (NPB) exhibit an ambipolar charge transport behavior and low voltage drift under both hole and electron injection.