bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photostimulable Fluorescent Nanoparticles for Biological Imaging
Authors: Osvet Andres , Milde Moritz , Dembski Sofia , Rupp Sabine , Gellermann Carsten , Batentschuk Miroslaw , Brabec Christoph J. , Winnacker Albrecht 
Published: September 2011

ABSTRACTSpherical monodisperse core/shell-type nanoparticles, comprising an amorphous SiO2 core coated with a luminescent phosphor layer were synthesized by the modified Pechini processes. The sol-gel method allows covering the 50 – 500 nm core particles with different inorganic phosphor layers of about 10 nm thickness, doped with rare-earth or transition metal ions which determine the luminescent properties. Particles comprising a Zn2SiO4 shell, doped with Mn2+ ions, are not only fluorescent under UV irradiation (260 nm), but store the activation energy by trapping electrons/holes at lattice defects. This energy is released as phosphorescence in the time scale of seconds and minutes, or as photostimulated luminescence under the excitation of red light (650 nm). Traps related to these processes are different, and their concentration is affected by the preparation conditions of the particles.
Electronic Structure Calculations Using A Modified Thomas-Fermi Approximation
Authors: Dente Gregory C. , Tilton Michael 
Published: September 2011

ABSTRACTWe have recently developed an accurate and easily implemented approach to many-electron calculations, based on a modified Thomas-Fermi approximation. Specifically, we derived an electron density approximation, the first term of which is the Thomas-Fermi result, while the remaining terms substantially corrected the density near the nucleus. In a first application, we used the new density to accurately calculate the details of the self-consistent ion cores, as well as the ionization potentials for the outer s-orbital bound to the closed-shell ion core of the Group III, IV and V elements. Next, we demonstrated that the new density expression allows us to separate closed-shell core electron densities from valence electron densities. When we calculated the valence kinetic energy density, we showed that it separated into two terms: the first exactly cancelled the potential energy due to the ion core in the core region; the second was the residual kinetic energy density resulting from the envelopes of the valence electron orbitals. These features allowed us to write a functional for the total valence energy dependant only on the valence density. This equation provided the starting point for a large number of electronic structure calculations. Here, we used it to calculate the band structures of several Group IV and Group III-V semiconductors. We emphasize that this report only provides a summary; detailed derivations of all results are in Reference 5.
Influence of Process Condition on the Dielectric Properties of CCTO-P(VDF-TrFE) 0-3 Composites
Authors: Shan Xiaobing , Zhang Lin , Cheng Z.-Y. 
Published: September 2011

AbstractA high dielectric constant was observed in 0-3 composites using P(VDF-TrFE) copolymer as matrix and CaCu3TiO4 (CCTO) ceramic powders as fillers with a composition of 50 vol% CCTO. CCTO-P(VDF-TrFE) 0-3 composites with a CCTO content from 0 to 50 vol% were prepared and their dielectric properties, including frequency dependence and temperature dependence of the dielectric constant and loss, were characterized. It was experimentally observed that the hot-press process, inlcuding the configuration and hot-press time, has a strong influence on the dielectric properties of the composites. Additionally, the influence of the CCTO partice size on the dielectric properties of the composites was studied.
Electrochromic performance of WO3 thin films with solvent-free viscous electrolytes based on polyethylene glycol-titanium oxide nanocomposites
Authors: Mendoza Narcizo , Hechavarría Liliana , Paraguay-Delgado Francisco , Hu Hailin 
Published: September 2011

ABSTRACTPolymeric nanocomposites of polyethylene glycol (PEG) with titanium oxide compound, PEG-Ti, have been prepared by sol-gel method from liquid PEG and titanium isopropoxide in acidic medium. Lithium salt (LiX) has been added into PEG-Ti to form PEG-Ti-LiX polymeric electrolytes. Electrochromic devices based on tungsten oxide thin films and PEG-Ti-LiX electrolyte may show excellent optical transmittance transient, however it depends on the type of lithium salt used during the sol-gel process. With LiI, the color change speed of the devices is very fast but they show a yellow color at bleaching state. The use of LiClO4 makes the devices totally transparent in visible region but the optical contrast is small. Possible molecular structure model of these polymeric electrolytes have been analyzed to explain the relation between electrochromic performance of tungsten oxide and electrolyte chemical composition.
Methods of Faience Manufacture in Antiquity: Investigation of Colorants and Technological Processes
Authors: Frame Lesley , DeSordao Donna Bright , Chiang Yuan-Chi , Vandiver Pamela 
Published: September 2011

ABSTRACTFaience production methods include efflorescence, direct glaze application, and cementation glazing. However, similar processing has been used with a variety of other materials, such as glazed monolithic quartz, ground and re-fired faience, and steatite bodies. Furthermore, faience technology has been linked by similar processing to glass, synthetic pigment and glazing technologies. Here we reinforce these cross-craft relationships by comparing the range of similar functioning chemical elements in faience and glazed artifacts from a variety of archaeological sites that range from the Indus Valley to the Mediterranean. This broad comparative method based primarily on x-ray fluorescence analysis reveals trends in faience production, relationships with metallurgical technologies, and aspects of processing that provide areas of study that may be considered more closely in the future.
Effect of Bandgap Grading on the Performance of a-Si1-xGex:H Single-Junction Thin-Film Solar Cells
Authors: Hsu H. J. , Wang C. M. , Hsu C. H. , Tsai C. C. 
Published: September 2011

ABSTRACTIn this work, the effect of bandgap grading of hydrogenated amorphous silicon germanium (a-Si1-xGex:H) absorber near the p/i and the i/n interfaces was investigated. The a-Si1-xGex:H single-junction solar cells were improved by applying both p/i grading and i/n grading. Our results showed that both the p/i and the i/n grading can increase the open-circuit voltage (VOC) as compared to the cell without grading. The i/n grading can further improve the FF. Presumably the potential gradient created by the i/n grading can facilitate the hole transport thus it can improve the FF. However, the JSC decreased as the i/n grading width increased. The reduction of JSC was due to the loss in the red response, which can be attributed to the replacement of lower bandgap material by the larger ones. Combining the effects of VOC, JSC and FF, a suitable thickness of the p/i and the i/n grading was 20 nm and 45 nm, respectively. Finally, the grading structures accompanied with further optimization of doped layers were integrated to achieve a cell efficiency of 8.59 %.
Formation of Light-weight Low-density Materials via Gas Phase Aerosol Gelation
Authors: Sorensen Christopher M. , Dhaubhadel Rajan , Gerving Corey S. , Chakrabarti Amitabha 
Published: September 2011

ABSTRACTWe have demonstrated that gas phase explosive combustion can lead to nanoparticle aerosols with sufficiently large volume fraction to cause a volume spanning gel to form on the order of ten’s of seconds. The term “aerosol gel” was coined to name these materials. So far we have made aerosol gels of carbon and silica. These aerosol gels are similar to well-known, liquid-phase, sol-gel synthesized aerogels.
Impact of rapid thermal annealing and hydrogenation on the doping concentration and carrier mobility in solid phase crystallized poly-Si thin films
Authors: Kumar A. , Widenborg P.I. , Hidayat H. , Zixuan Qiu , Aberle A.G. 
Published: September 2011

ABSTRACTThe effect of the rapid thermal annealing (RTA) and hydrogenation step on the electronic properties of the n+ and p+ solid phase crystallized (SPC) poly-crystalline silicon (poly-Si) thin films was investigated using Hall effect measurements and four-point-probe measurements. Both the RTA and hydrogenation step were found to affect the electronic properties of doped poly-Si thin films. The RTA step was found to have the largest impact on the dopant activation and majority carrier mobility of the p+ SPC poly-Si thin films. A very high Hall mobility of 71 cm2/Vs for n+ poly-Si and 35 cm2/Vs for p+ poly-Si at the carrier concentration of 2×1019 cm-3 and 4.5×1019 cm-3, respectively, were obtained.
Excimer-Laser-Induced Melting and Solidification of PECVD a-Si films under Partial-Melting Conditions
Authors: Hu Q. , Lee Catherine S. , Li T. , Deng Y. , Chung U.J. , Limanov A. B. , Chitu A. M. , Thompson M.O. , Im James S. 
Published: September 2011

ABSTRACTThis paper reports on new experimental findings and conclusions regarding the pulsed-laser-induced melting-and-solidification behavior of PECVD a-Si films. The experimental findings reveal that, within the partial-melting regime, these a-Si films can melt and solidify in ways that are distinct from, and more complex than, those encountered in microcrystalline-cluster-rich LPCVD a-Si films. Specifically (1) spatially dispersed and temporally stochastic nucleation of crystalline solids occurring relatively effectively at the moving liquid-amorphous interface, (2) very defective crystal growth that leads to the formation of fine-grained Si proceeding, at least initially after the nucleation, at a sufficiently rapidly moving crystal solidification front, and (3) the propensity for local preferential remelting of the defective regions and grain boundaries (while the beam is still on) are identified as being some of the fundamental factors that can participate and affect how these PECVD films melt and solidify.
Investigation of local light scattering properties of thin-film silicon solar cells with subwavelength resolution
Authors: Bittkau K. , Hoffmann A. , Owen J. , Carius R. 
Published: September 2011

ABSTRACTIn order to obtain efficient light trapping within a thin-film silicon solar cell, randomly textured interfaces are used. The texture can be introduced by wet-chemical etching in diluted hyrdofluoric acid (HF). By varying of the HF concentration, a continuous transition to smaller surface structures can be achieved. Near-field scanning optical microscopy is applied to measure scattered light with sub-wavelength resolution. On those different surfaces, using Fourier high-pass filters on the measured near-field images, surface features with a high light trapping potential are identified. Finally, criteria for optimized scattering surfaces are obtained.
Amorphous Silicon Based Particle Detectors
Authors: Wyrsch N. , Franco A. , Riesen Y. , Despeisse M. , Dunand S. , Powolny F. , Jarron P. , Ballif C. 
Published: September 2011

ABSTRACTRadiation hard monolithic particle sensors can be fabricated by a vertical integration of amorphous silicon particle sensors on top of CMOS readout chip. Two types of such particle sensors are presented here using either thick diodes or microchannel plates. The first type based on amorphous silicon diodes exhibits high spatial resolution due to the short lateral carrier collection. Combination of an amorphous silicon thick diode with microstrip detector geometries permits to achieve micrometer spatial resolution beneficial for high accuracy beam positioning. Microchannel plates based on amorphous silicon were successfully fabricated and multiplication of electrons was observed. This material may solve some of the problems related to conventional microchannel devices. Issues, potential and limits of these detectors are presented and discussed.
Band alignment at amorphous/crystalline silicon hetero-interfaces
Authors: Korte L. , Schulze T. F. , Leendertz C. , Schmidt M. , Rech B. 
Published: September 2011

ABSTRACTWe present an investigation of the band offsets in amorphous/crystalline silicon heterojunctions (a-Si:H/c-Si) using low energy photoelectron spectroscopy, ellipsometry and surface photovoltage data. For a variation of deposition conditions that lead to changes in hydrogen content and the thereby the a-Si:H band gap by ∼180 meV, we find that mainly the conduction band offset ΔEV varies, while ΔEC stays constant within experimental error. This result can be understood in the framework of charge neutrality (CNL) band lineup theory.
Excitation of guided-mode resonances in thin film silicon solar cells
Authors: Haug F.-J. , Söderström K. , Naqavi A. , Ballif C. 
Published: September 2011

ABSTRACTThin film silicon solar cells are attractive for photovoltaics; however, the poor charge transport in this material requires that the devices are thinner than the absorption length. Adequate absorption can nevertheless be achieved by light scattering at textured interfaces because light can get trapped inside the absorber layer if it is scattered into angles above the critical angle of total internal reflection. This situation can be identified with the propagation of a guided mode in a waveguide where silicon plays the role of the high index guiding medium and the interface texture serves to couple the incident light to modes via grating coupling. We present an experimental realization of a solar cell structure on a line grating where the enhanced photocurrent can be clearly related to resonant excitation of waveguide modes.
DC and AC Gate-Bias Stability of Nanocrystalline Silicon Thin-Film Transistors Made on Colorless Polyimide Foil Substrates
Authors: Chiu I-Chung , Cheng I-Chun , Chen Jian Z. , Huang Jung-Jie , Chen Yung-Pei 
Published: September 2011

ABSTRACTStaggered bottom-gate hydrogenated nanocrystalline silicon (nc-Si:H) thin-film transistors (TFTs) were demonstrated on flexible colorless polyimide substrates. The dc and ac bias-stress stability of these TFTs were investigated with and without mechanical tensile stress applied in parallel to the current flow direction. The findings indicate that the threshold voltage shift caused by an ac gate-bias stress was smaller compared to that caused by a dc gate-bias stress. Frequency dependence of threshold voltage shift was pronounced in the negative gate-bias stress experiments. Compared to TFTs under pure electrical gate-bias stressing, the stability of the nc-Si:H TFTs degrades further when the mechanical tensile strain is applied together with an electrical gate-bias stress.
Modeling of Advanced Light Trapping Approaches in Thin-Film Silicon Solar Cells
Authors: Zeman Miro , Isabella Olindo , Jäger Klaus , Babal Pavel , Solntsev Serge , Santbergen Rudi 
Published: September 2011

ABSTRACTDue to the increasing complexity of thin-film silicon solar cells, the role of computer modeling for analyzing and designing these devices becomes increasingly important. The ASA program was used to study two of these advanced devices. The simulations of an amorphous silicon solar cell with silver nanoparticles embedded in a zinc oxide back reflector demonstrated the negative effect of the parasitic absorption in the particles. When using optical properties of perfectly spherical particles a modest enhancement in the external quantum efficiency was found. The simulations of a tandem micromorph solar cell, in which a zinc oxide based photonic crystal-like multilayer was incorporated as an intermediate reflector (IR), demonstrated that the IR resulted in an enhanced photocurrent in the top cell and could be used to optimize the current matching of the top and bottom cell.
Recent progress in transparent conducting materials by use of metallic grids on metaloxides
Authors: van Deelen Joop , Rendering Henk , Hovestad Arjan 
Published: September 2011

ABSTRACTAlternatives to ITO are under heavy investigation. Organic and inorganic transparent conducting materials are compared based on their transparency versus sheet resistance characteristics. Although graphene has advanced recently, TCOs are still superior in performance and can only be surpassed by the combination of transparent materials with a metal grid. Results on modeling and design optimization using a monolithically integrated CIGS cell configuration as case showed that considerable efficiency enhancement (up to 17% in power output compared to single TCOs) can be achieved for metal grid/TCO combinations. Conductivity improvement has been experimentally verified by four point probe measurements. on both commercial ITO coated PET foil as well as on ZnO coated glass with electrochemically deposited metal grids Sheet resistances as low as 0,1 Ohm/sq were reached and 80 times and 400 times conductivity improvements were obtained at a transparency loss of only 3% and 6%, respectively. It was also found that electrochemical deposition results in more conductive grids than obtained by Ag-ink screen printing due to higher aspect ratios and bulk-like conductivity of the first. Simultaneously, nanopatterning allows optimal grid width of 20 μm, as determined by modeling.
Fabrication of Improved p-AgGaSe2/n-Si Heterojunction Solar Cells on Optimum Quality Thermally Evaporated AgGaSe2 Thin Films
Authors: Das Sandip , Mandal Krishna C. 
Published: September 2011

ABSTRACTOptimum quality polycrystalline AgGaSe2 thin films were deposited on H-terminated n-Si substrates by controlled thermal evaporation method. The film deposition conditions were varied to optimize the structure and optoelectronic properties of AgGaSe2 thin films. X-ray diffraction (XRD) studies showed that all AgGaSe2 films were of chalcopyrite structure and while the films deposited at room temperature (300 K) had random grain orientation, the films deposited at higher substrate temperature (≥ 450K) showed preferred (112) orientation. The composition of the films were analyzed by electron probe microanalysis (EPMA) deposited at different substrate temperatures. The ultraviolet-visible (UV-Vis) spectra showed the optical bandgap of 1.80 eV, with sharper band edge for the films deposited at higher temperature. The films were p-type and the resistivities of the as deposited films at 300 and 650K were ~5×103 and ~200 Ω.cm respectively. p-AgGaSe2/n-Si heterojunction solar cells, having an active area of 0.18 cm2 without any antireflection coating were designed and fabricated. It was observed that the films deposited at 650K produced heterojunctions with significantly improved photovoltaic properties. The evidence of the barrier height modifications have been provided by C-V measurements. Under solar simulator AM1 illumination, the improved junction exhibited an efficiency of 5.2%, whereas the AgGaSe2 films deposited at 300K showed a lower efficiency of 2.1%.
High Throughput, Low Cost Deposition of Alumina Passivation Layers by Spatial Atomic Layer Deposition
Authors: Vermeer Ad , Roozeboom F. , Poodt P. , Gortzen Roger 
Published: September 2011

ABSTRACTAtomic Layer Deposition (ALD) is a gas phase deposition technique for depositing very high quality thin films with an unsurpassed conformality. The main drawback of ALD however is the very low deposition rate (~ 1 nm/min). Recently, record deposition rates for alumina of up to 1 nm/s were reached using spatial ALD, while maintaining the typical assets regarding film quality as obtained by conventional, slow ALD [1]. This allows for ALD at high throughput numbers.One interesting application is passivation of crystalline silicon solar cells. Applying a thin alumina layer is reported to increase solar cell efficiency and enables the use of thinner wafers, thus reducing the main cost factor [2]. In this paper we report on the latest progress made by SoLayTec that delivered a working prototype of a system realizing full area single sided deposition of alumina on 156 x 156 mm2, mono- and multi crystalline silicon wafers for solar cell applications. The alumina layers showed excellent passivation. Based on this concept, a high-throughput ALD deposition tool is being developed targeting throughput numbers of up to 3000 wafers/hr, making ALD ready for mass production. This will bring on new opportunities in other applications.
I-III-VI2 (Copper Chalcopyrite-based) Thin Films for Photoelectrochemical Water-Splitting Tandem-Hybrid Photocathode
Authors: Kaneshiro Jess M. , Deangelis Alexander , Song Xi , Gaillard Nicolas , Miller Eric L. 
Published: September 2011

ABSTRACTThis presentation will investigate various parameters regarding the use of I-III-VI2 Copper Chalcopyrite-based materials for use in tandem-hybrid photocathodes capable of splitting water into hydrogen and oxygen gases in an acidic electrolyte. Constituent parts (fabricated at HNEI) of a proposed monolithically integrated hybrid photovoltaic/photoelectrochemical (PV/PEC) device were characterized separately and combined theoretically using electronic and optical models to simulate tandem operation to first indicate feasibility of matching existing materials. Robust CGSe2 photocathodes were focused on for the PEC cells and CIGSe2 and CISe2 devices were evaluated for the PV cells. Simulation suggested the hybrid PV/PEC system could pass enough light to produce up to 15.87mA/cm2, validating the feasibility and warranting the fabrication of stacked PV/PEC devices.
Fabrication of High Efficiency Flexible CIGS Solar Cell with ZnO Diffusion Barrier on Stainless Steel Substrate
Authors: Dowon Bae , Sehan Kwon , Joonjae Oh , Joowon Lee , Wookyoung Kim 
Published: September 2011

ABSTRACTi-ZnO layers were deposited as diffusion barriers fabricated by RF sputtering on stainless-steel substrates (SUS430, matches with AISI SUS24). It was found that the addition of ZnO layer between stainless-steel substrate and Mo back contact film deplete diffusion of metal ions from substrate and reduce recombination at CIGS layer, as identified by an SIMS depth profile, QE and C-V measurements. With such diffusion barriers, the efficiency, open-circuit voltage, short-circuit current and fill factor of CIGS solar cells all increased, compared to reference cells without diffusion barrier. For the better device performance, Na was supplied during Mo back-contact layer deposition by co-sputtering of the target, including Na-source. Efficiencies of cells were increased with increasing the quantity of Na source. Unlike barrier thickness effect, short circuit current was reduced and open circuit voltage, fill factor were increased with increasing Na-source, and achieved 12.6% efficiency without AR(anti-reflection) coating. The relationship and causality between these results and the Na-doping were analyzed using C-V measurements.
New MEH-PPV Based Composite Materials for Rewritable Nonvolatile Polymer Memory Devices
Authors: Dronov Mikhail , Belogorohov Ivan , Khokhlov Dmitry 
Published: September 2011

ABSTRACTWe present the memory performance of devices with bistable electrical behavior based on MEH-PPV (Poly (1-methoxy-4-(2-ethylhexyloxy)-p-phenylenevinylene)) containing metal (Zn or Fe-Ni) particles. Another memory device based on aluminum phthalocyanine chloride (PcAlCl) added to the composite material reveals the photoinduced switching, in addition to the electrical one. Possible mechanisms for resistive switching are discussed.