bluuebunny/crossref_metadata_2025_split huggingface dataset:
Novel Memory Effect Found in Nematic Liquid Crystal/Clay Mineral Composites
Authors: Kawasumi M. , Hasegawa N. , Usuki A. , Okada A. , Kurauchi T. 
Published: April 2011

AbstractNovel liquid crystalline composites composed of a nematic two-frequency-addressing liquid crystal and organized clay mineral have been prepared. The particles of the clay mineral were dispersed homogeneously in the liquid crystal. The composite cells displayed a reversible and multistable electro-optical effect between transparent and turbid light scattering states by changing the frequency of the electric field. The light transmittances of both transparent and light scattering memory states did not change after 15 hrs without the electric field applied.
The Effect of Hydrogen Bonding on the Mesomorphic Properties for Side Chain Type Liquid Crystalline Polyurethanes
Authors: Mihara T. , Koide N. 
Published: April 2011

AbstractMesomorphic properties and temperature dependence of the hydrogen bonding between urethane bonds (H-bonding) for side chain type liquid crystalline polyurethane(SLCPU)s were studied by thermally controlled FT-IR spectroscopy. A remarkable change in the strength of H-bonding for SLCPUs with a flexible chain in the polymer backbone(flexible SLCPUs) was displayed near the phase transition temperatures, while small changes in the strength of H-bonding for SLCPUs with a rigid moiety in the polymer backbone(rigid SLCPUs) was influenced by a mesogenic group in the side chain and the flexible chain length in the polymer backbone. Furthermore, in order to study the influence of H-bonding in rigid SLCPUs, polyurethane derivatives with methyl group were synthesized replacing hydrogen in urethane bonds. No mesomorphic properties for polyurethane derivatives obtained were exhibited. It was concluded that H-bonding played an important role to exhibit mesomorphic properties of rigid SLCPUs.
Synthesis and Study of 4'-Acyl-4-Biphenylol Esters
Authors: Lu Wan-Fang , Zhang Zhi-Yong , Ding Hui , Shi Yao-Zeng 
Published: April 2011

AbstractEight new 4'-acyl-4-biphenylol esters 5a∼h were synthesized and their mesomorphic properties were tested by PM and DSC. These compounds have wider mesomorphic transition temperature ranges and higher clearing points. The compound 5g in which there is no chiral carbon exhibits a stripped focal conic texture in its Sc mesophase. The effect of the molecular structure on the liquid crystal properties was discussed.
Comparison of Vapor Phase and Liquid Phase Epitaxy for Deposition of Crystalline Si on Glass
Authors: Kühnle J. , Bergmann R. B. , Krinke J. , Werner J. H. 
Published: April 2011

AbstractWe compare the suitability of vapor phase and liquid phase epitaxy in a two step deposition process for the formation of thin crystalline Si films on glass substrates. In a first deposition step, we form polycrystalline Si seeding layers on glass. In a second step, we increase the thickness either by vapor phase or liquid phase epitaxy. Liquid phase epitaxy leads to growth of faceted grains of more than 100 μm in diameter but the films are not continuous. In contrast, chemical vapor deposition results in continuous, smooth films with grain sizes up to 7 μm. This difference of morphology originates from the influence of supersaturation and growth rate anisotropy. Chemical vapor deposited films exhibit surface morphologies and electrical properties that are promising for the preparation of crystalline thin film Si solar cells.
Development of Cu(InGa)Se2 Thin Film Solar Cells with Cd-Free Buffer Layers
Authors: Konagai M. , Ohtake Y. , Okamoto T. 
Published: April 2011

AbstractCu(InGa)Se2(CIGS) thin film absorbers were fabricated by a three-stage method using a coevaporation apparatus. As a Cd-free buffer layer, ZnSe, InxSe, GaxSey and ZnInxSey buffer layers have been deposited on the CIGS absorber continuously in the same apparatus. Atomic layer deposition (ALD) was employed as a growth technique for ZnSe. This technique offers a good thickness control as well as a good surface coverage. By irradiating with a solar simulator, all the solar cell parameters increased drastically for the first 50 minutes of the irradiation and then saturated at longer irradiation times. This phenomenon did not appear for the cells with a CdS buffer layer. The best efficiency of ZnO/ZnSe/CIGS thin film solar cells with about 10 nm thick ZnSe buffer layer was 11.6%. On the other hand, ZnO/InxSey/CIGS thin film solar cells showed very stable characteristics under the light illumination, and initial measurements show an efficiency of 13.0%.
Measured and Simulated Temperature Dependence of A-Si:H Solar Cell Parameters
Authors: Stiebig H. , Eickhoff Th. , Zimmer J. , Beneking C. , Wagner H. 
Published: April 2011

AbstractIn contrast to the successful application of analytic equations to the current-voltage behaviour of crystalline silicon solar cells in the dark and under AM1.5 illumination, the description of a-Si:H solar cells parameters requires device modelling concepts taking the full set of semiconductor equations into account. This in particular holds for the explanation of the temperature dependence (225–400K) of experimentally determined a-Si:H p-i-n solar cell parameters. Device modelling calculations show that the observed decrease of the short circuit current at AM 1.5 with lower T is much more effected by the additional charge trapped in the tail states and recharging of defect states than by the broadening of the gap. The induced electric field distortion blocks the extraction of photo generated holes. The open circuit voltage Voc increases with lower T which is caused by the same trapping effect.
Use of Super-Thin Modulated Reactants to Influence Binary Intermediate Formation in Thin Film CuInSe2 Synthesis
Authors: Musialowski M. , Guffey S. , Hornbostel M. D. , Johnson D. C. 
Published: April 2011

AbstractA multilayer synthesis of polycrystalline CuInSe2 has been performed by vacuum evaporation with repeat layers thinner than 225Å. Samples deposited with different elemental sequences and repeat layer thicknesses were analyzed by x-ray diffraction as a function of annealing temperature. Samples with 225Å layers produce multiple phases in the synthetic pathway. In samples with thinner layers small amounts of In2Se3 were detected but CuInSe2 predominated. Diffraction and calorimetry data indicate that CuInSe2 and In2Se3 crystallites begin growth at room to moderate temperatures. Layering of samples was probed by grazing angle x-ray diffraction and similarly indicates interdiffusion of layers at room to moderate temperatures.
Growth and Characterization of Copper Indium Diselenide Thin Films by Molecular Beam Deposition
Authors: Ueng H. Y. , Chang D. Y. , Lin J. L. 
Published: April 2011

AbstractCuInSe2 thin films grown on Corning 7059 glass substrates were prepared by molecular beam deposition method with various Cu/In ratios in order to study the relationship between composition and material properties. Under a fixed copper beam flux intensity and overpressure selenium environments, the composition of films was modulated by changing the indium beam flux: intensity to obtain Cu-rich or In-rich films. The X-ray diffraction patterns show that the epitaxy films grown onto glass substrates are the polycrystalline structure. The grain size of polycrystalline films indicate that the surface morphology of the films are varied as a function of Cu/In ratio.
The Effects of Air Annealing on Cuinse2 Thin Films Grown by Molecular Beam Fpitaxy
Authors: Kim I. , Niki S. , Fons P. J. , Kurafuji T. , Okutomi M. , Yamada A. 
Published: April 2011

AbstractHigh quality epitaxial CuInSe2 (CIS) films with a range of Cu/In ratios (γ) = 0.80∼2.24 grown by molecular beam epitaxy (MBE) have been post-annealed at temperatures of TA=200∼400°C in both dry-air and Ar atmospheres. Changes in the structure and composition due to annealing have been investigated. The only oxide observed experimentally for both the In-rich, and the Cu-rich CIS films was In2O3. This is consistent with equilibrium thermodynamic calculations which indicate that In2O3 is the mnst stable solid oxide phase. During annealing some reac-tions arc probably kinetically limited making the annealing process a function of time and temperature. but the equilibrium thermodynamic results reported here simplify interpretation of phase space.
Surface Characterization of Cu(In, Ga)Se2 Thin Films Treated by Various Solutions
Authors: Wada T. , Hashimoto Y. , Kusao K. , Kohara N. , Negami T. , Nishitani M. 
Published: April 2011

AbstractCu-rich Cu(In, Ga)Se2 (CIGS) films were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive x-ray fluorescence spectroscopy (EDX) and x-ray photoelectron spectroscopy (XPS). The Cu-rich CIGS film were treated in KCN and NH3 solutions. In the as-deposited Cu-rich CIGS film, the cation ratio of Cu/(In+Ga) at the surface exceeded the bulk value. Cross-sectional TEM of the KCN-treated film suggested that Cu2-xSe existed both at the grain boundaries and on the grains near the surface of the Cu-rich CIGS film. The Cu2-xSe was completely removed by the treatment in the KCN solution and was removed only at the front surface by treatment in the NH3 solution.
Electrical Properties of Coevaporated CuInS2 Films by in-situ Conductivity Measurements
Authors: Scheer R. , Alt M. , Luck I. , Schieck R. , Lewerenz H. J. 
Published: April 2011

AbstractThe conductivity σ of CuInS2 films grown by coevaporation is investigated by in-situ measurements during the deposition and ex-situ measurements. During the controlled cool-down period of the grown films, σ vs l/T data are obtained for films with Cu-rich and In-rich composition. Furthermore, first experiments on the effect of extrinsic dopants such as P, N, and Na on the conductivity of In-rich films are reported.
CdTe Thin Films: Spray Deposition Using a Nanoparticle Ink Precursor
Authors: Schulz Douglas L. , Pehnt Martin , Curtis Calvin J. , Ginley David S. 
Published: April 2011

AbstractCdTe thin film growth using nanoparticle precursors and spray deposition has been investigated. Employing a metathesis approach, cadmium iodide was reacted with sodium telluride in methanol solvent resulting in the formation of soluble Nal and insoluble CdTe nanoparticles. After appropriate chemical workup, methanol-capped CdTe colloids were isolated. CdTe colloids prepared by this method exhibit a dependence of the nanoparticle diameter upon reaction temperature as determined by transmission electron microscopy (TEM) and UV-Visible spectroscopy (UV-Vis). CdTe thin film formation was achieved by spray depositing the nanoparticle colloids (25–75 Å diameter) onto substrates at elevated temperatures (T = 280–440 °C) with no further thermal treatment. These films were characterized by XRD, x-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Cubic CdTe phase formation was observed by XRD with a contaminant oxide phase also detected. XPS analysis showed that CdTe films produced by this one-step method contained no Na or C, but substantial O. AFM gave CdTe grain sizes of ˜0.1–0.3 pim for films sprayed at 400 °C. A layer-by-layer film growth mechanism proposed for the one-step spray deposition of nanoparticle precursors will be discussed.
Effects of Rapid Thermal Annealing on CdTe/CdS Solar Cell Fabrication
Authors: Cho Y. A. , Nam W. J. , Kim H. S. , Yeom G. Y. , Yoon J. K. , Oho K. H. , Shin S. H. , Park K. J. 
Published: April 2011

AbstractRapid thermal annealing (RTA) was applied to anneal polycrystalline CdTe thin films evaporated on CdS/ITO substrate and the effects of rapid thermal annealing temperatures and gas environments were studied. X-ray diffractometer (XRD), X-ray photoelectron spectroscopy(XPS), energy dispersive X-ray spectroscopy(EDX), cross-sectional transmission microscopy(TEM), and micro-EDX in TEM were used to characterize physical and chemical properties of rapid thermal annealed CdTe thin films. Complete CdTe/CdS photovoltaic cells were fabricated and I-V characteristics of these cells were measured under the illumination. Results showed that the bulk composition of CdTe remained stoichiometric to 550°C in the air environment and surface composition became Cd-rich. Cross-sectional TEM and micro-EDX showed columnar grains and micro-twins remained even after RTA, however, sulfur content in rapid thermal annealed CdTe caused by sulfur diffusion from CdS during the annealing was much smaller than that by furnace annealing. Among the investigated RTA temperatures and gas environments, the cell made with CdTe annealed at 550°C in the air showed the best solar energy conversion efficiency.
Effect of CdTe Stoichiometry on the Electrical Properties of CdTe Films
Authors: Chung Gil Yong , Song Jin Soo , Ahn Byung Tae 
Published: April 2011

AbstractCdTe films have been prepared by a close-spaced sublimation (CSS) process with screenprinted CdTe layers as a source. The electrical resistivity of the CdTe film deposited in O2 was about one order of magnitude lower than that of the film deposited in He. The Cd content in the CdTe films deposited in O2 was smaller than that in the CdTe films deposited in He. No oxygen was detected in the CdTe films deposited in O2. As the Cd/Te ratio decreased, the resistivity of the CdTe films decreased and reached at about 3×104 Ω2.cm. The resistivity decrease by oxygen flow was diminished when the CdTe composition was limited by solid solubility. The above results indicated that the resistivity decrease of CdTe films deposited in O2 was not by due to the oxygen doping but by due to the CdTe stoichiometry change.
Hydrogen Treatment of Undoped Zno Thin Film Using Photo-Chemical Vapor Deposition
Authors: Baik Seung Jae , Song Jinsoo , Lim Koeng Su 
Published: April 2011

AbstractTo obtain high quality ZnO thin films for use as transparent electrodes of amorphous silicon solar cells, hydrogen treatment of the films using photo-chemical vapor deposition was performed for the first time. The as-deposited ZnO thin film was irradiated by UV light during the flow of hydrogen molecules in the presence of photo-sensitizers of mercury. As the treatment time increased, resistivity decreased from 1 × 10−2Ωcm to 2 × 10−3Ωcm. Moreover, haze ratio increased from 20% to 48%. Hydrogen radicals were thought to be playing various roles on the neighborhood of the surface region and the grain boundary region.
This new trial gave us new understanding into the relation between hydrogen and ZnO. Moreover, these results could be applied to the process of amorphous silicon solar cells and a possible increase of efficiency is expected.
Photoinduced Reversible Conductivity and Photoconductivity Changes in Transparent Amorphous and Micro-Crystalline In2O3-X Films
Authors: Stradins P. , Fritzsche H. , Claflin B. 
Published: April 2011

AbstractThe dark conductivity σ of poorly conducting In2O3-x films can be enhanced by orders of magnitude by blue or UV light exposure at any temperature between 4.2K and 300K. The resulting high σ state of amorphous films reverts back to its original low σ state upon heating to 400K in an inert gas and can be repeated many times. In crystalline films the high σ state is stable to higher temperatures where annealing leads to some outdiffusion of oxygen and hence to a conductivity increase which can only be reversed by external re-oxidation. The photoinduced increase in dark conductivity is accompanied by an increase in photoconductivity at hv = 0.6 or 2eV by a factor of 107 at 4.2K.
Ale Growth of Transparent Conductors
Authors: Rit Mikko , Asikainen Timo , Leskelä Markku , Skarp Jarmo 
Published: April 2011

AbstractOwing to its self-limiting growth mechanism the Atomic Layer Epitaxy (ALE) technique is capable of growing uniform high quality thin films on large area substrates. Therefore, ALE is an attractive choice for depositing transparent electrically conducting films for large area applications, such as solar cells and flat panel displays. In this paper studies on ALE growth of In2O3 and ZnO based transparent conducting thin films will be presented. In2O3, In2O3:Sn and In 2O3:F films were grown at 500 °C and their lowest resistivities were about 3 x 10-3, 2 x 10-3 and 6 x 10-4 Ωcm, respectively. Low temperature (120 - 350 °C) ALE deposition processes were developed for ZnO and ZnO:AI films, the latter having resistivities as low as 8 x 10-4 Ωcm. A straightforward scale-up of the ZnO process from 5 x 5 to 30 x 30 cm 2 substrate size was also demonstrated.
Nano-Scale Resolved Detection of Photo-Current in a-Si:H Films
Authors: Koida Takashi , Kawasaki Masashi , Maruyama Ryuichiro , Matsuse Mitsutaka , Koinuma Hideomi 
Published: April 2011

AbstractThe growth mode of a-Si:H plasma CVD film was observed by AFM to range from homogeneous deposition to heterogeneous island formation depending on the substrate material and deposition temperature. The correlation between the grain-like structure and electric property of the film deposited on transparent conductive SnO2 substrates has been elucidated by using an AFM with a conductive cantilever. The local distribution of photo-current in the a-Si:H films was found to agree well with the topographic image; the photo-current around the grain boundaries was lower than that on the grains. The effect of surface treatment with an aqueous HF solution indicates that the imhomogeneity in the photo-current originates from the preferential oxidation around the grain boundaries rather than intrinsic electric property.
A Simple Optical Properties Modeling of Microcrystalline Silicon by the Effective Medium Approximation Method
Authors: Cho Woo Yeong , Lim Koeng Su , Cho Hyun-Mo 
Published: April 2011

AbstractThe optical properties of microcrystalline silicon (µc-Si) were estimated using the EMA (Effective Medium Approximation) method. This modeling was based on two-phase mixture, amorphous silicon (a-Si) and crystalline silicon (c-Si) with volume fractions of fa and fc respectively. From this modeling, it could be possible to understand thatµc-Si has lower light absorption characteristics than a-Si over all solar spectrum by considering hydrogen involvement in embedded a-Si part of iic-Si and crystalline volume fraction. Also, it is proposed that p-type pe- Si is superior to n-type tic-Si because of its high optical gap of Eo4 and its low absorption coefficient spectrum shape.
Porous Semiconductor Films For Photo-Electrical Applications
Authors: Könenkamp R. , Hoyer P. 
Published: April 2011

AbstractWe report on the preparation and characterization of semiconductor devices based on porous nano-crystalline TiO2 films. We present experimental results on photoconduction to elucidate the role of trap states in this material. We then analyse the behavior of a SnO2/TiO2/Pt Schottkydiode and finally present spectral photoresponse data obtained on a hetero-junction between TiO2 films and PbS quantum dots. We find that the porous films hold some promise for electronic applications, in which fast reponse times are not required.
Monograin Powders And Layers For Photovoltaic Application
Authors: Altosaar M. , Mellikov E. , Hie J. , Meissner D. , Varema T. 
Published: April 2011

AbstractThe recrystallization of CdTe powders in different fluxes was studied and the possibility to grow p- and n - type CdTe monograin powders of high conductivity was shown. It was determined that very important technological factors for creating p - type conductivity in CdTe are the cooling rate and the presence of Te in flux. NaCl content in CdCl2 flux was found to inhibit the crystal growth and to allow for doping CdTe with Na that acts as an effective acceptor impurity in CdTe. The region of most effective added Na concentrations was found.
A New Confocal Scanning Laser MACROscope/Microscope Applied to the Characterization of Solar Cells
Authors: Ribes A. C. , Damaskinos S. , Tiedje H. F. , Dixon A. E. , Brodie D. E. , Duttagupta S. P. , Fauchet P. M. 
Published: April 2011

AbstractScanning stage microscopes have traditionally been used to provide high resolution, large area photocurrent mapping of solar cells and detectors. This imaging method, while very useful in the characterization and quality control of solar cells, is unfortunately slow (image acquisition takes several minutes). This paper describes a confocal scanning beam MACROscope-Microscope which can image specimens from 25×25 μm up to 7.5×7.5 cm in size, a zoom factor of 3000, using reflected light, photoluminescence, and optical beam induced current in less than 10s. Resolutions range from 0.25 to 10 μ;m laterally and 0.5 to 300 pm axially depending upon whether microscope or MACROscope mode is used. This instrument can therefore be used to characterize and provide quick and efficient quality control for solar cells and detectors at a microscopic and macroscopic level.A brief description of the MACROscope-Microscope is given. The MACROscope- Microscope's many abilities are highlighted by showing various reflected-light, photolhminescence and optical beam induced current images from CdZnS/CulnSe2 thin film solar cells and porous silicon devices.
Photovoltaic Effect in a-Si/c-Si Heterostructure Prepared by RF Magnetron Sputtering Technique
Authors: Budaguan B. G. , Sherchenkov A. A. , Aivazov A. A. 
Published: April 2011

AbstractPhotosensitivity spectral dependencies of the a-Si(n-type)/c-Si(p-type) heterostructure for the different reverse biases, Vb, amorphous Si film thickness, substrate predeposition temperatures, Ts, and annealing conditions, Ta, were investigated in the wavelengths range of 500–1200 nm It was found that the position of the relative photosensitivity maximum depends on Ts, and Vb and can be varied in the wavelengths range of 840–1080 nm. The energy band diagram of the heterostructure was analyzed to explain the observed results. It was shown that the photosensitivity properties of the a-Si/c-Si heterostructure depend on the interfacial condition. The perspective application of the structures investigated is IR detector fabrication.
Current Dependence of Reversible Electromigration Induced Resistance Changes in Short Al Lines and Interpretation of Irreversible Effects
Authors: Verbruggen A. H. , Van Den Homberg M. J. C. , Kalkman A. J. , Kraayeveld J. R. , Willemsen A. W.-J. , Radelaar S. 
Published: April 2011

AbstractChanges in the electrical resistance induced by electromigration in short (< 20 μm) Al lines show a rather well-defined behavior. For current densities j below a critical value jc the resistance change saturates with time and the resistance fully recovers when the current is switched off. Above the critical current density the induced resistance changes do not saturate and vary approximately linearly with time. In this case the resistance changes recover only partially after removal of the current. We report (i) measurements of the current dependence of the magnitude of the reversible resistance changes and (ii) the results of atomic force microscopy (AFM) inspection of the lines after stressing with current densities above jc. The resistance measurements were made with a high-resolution AC bridge technique. The samples were pure, unpassivated Al lines with a film thickness of 100 nm and a line width of 2 gm. The results show a linear dependence between the magnitude of the reversible changes and the current density. The linear dependence is predicted by two models. The first is based on a description of the vacancy flux and the second on a description of the build-up of mechanical stress during an electromigration experiment. To study the origin of the irreversible effects, samples were stressed at current densities above jc, and the induced irreversible changes in the resistance were recorded. Both negative and positive changes of the resistance were observed. After six hours the experiment was stopped and the lines were inspected by atomic force microscopy. It was always possible to observe a void, a hillock or a hillock/void pair that was created during the passage of the DC current. Moreover, lines with decreasing resistance during stress always showed a hillock and lines with an increased resistance always showed a void.