bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermoelectric Materials Discovery Using Combinatorial Chemistry
Authors: Amani Matin , Tougas Ian , Gregory Otto J. 
Published: September 2011

ABSTRACTTransparent conducting oxides have been previously investigated for both bulk and thin film thermoelectric applications, and have shown promising results due to their thermal stability and electrical conductivity. Alloys of two or more transparent conducting oxides have been deposited using pulsed laser deposition (PLD) and combinatorial sputtering, and the resulting films were optimized for optical applications. In this study, thermoelectric materials were prepared by co-sputtering techniques, whereby a chemical gradient was formed across an alumina substrate that was patterned using photolithography to form hundreds of micro-thermocouples. The systems indium tin oxide (ITO), indium zinc oxide (IZO), and zinc tin oxide (ZTO) were investigated for this purpose and the resulting combinatorial libraries were rapidly screened to establish room temperature resistivity, Seebeck coefficient, and power factor as functions of both composition and heat treatment, in nitrogen and air ambients. Due to their chemical stability, oxidation resistance, and large Seebeck coefficients relative to metal thermocouples, these materials are ideal for temperature measurement or energy harvesting in harsh environments such as gas turbine engines.
Optoelectronic characterization of morphology-controlled zinc oxide nanowires
Authors: Kuo Shou-Yi , Lai Fang-I , Wang Chun-Chieh , Lin Woei-Tyng 
Published: September 2011

ABSTRACTIn this paper, we report the characterization of vertically aligned ZnO nanowire (NW) arrays synthesized by metal-catalyzed chemical vapor deposition. The growth mechanism of ZnO NWs may be related to vapor-solid-nucleation. Morphological, structural, optical and field emission characteristics can be modified by varying the growth time. For growth time reaches 120 min, the length and the diameter of ZnO NWs are 1.5 μm and 350 nm, and they also show preferential growth orientation along the c-axis. Moreover, strong alignment and uniform distribution of ZnO NWs can effectively enhance the antireflection to reach the average reflectance of 5.7% in the visible region as well. Field emission measurement indicated that the growth time play an important role in density- and morphology-controlled ZnO NWs, and thus ZnO NWs are expected to be used in versatile optoelectronic devices.
Thermochromism of VO2 Nanoparticles: Calculated Optical Properties and Applications to Energy Efficient Windows
Authors: Li S.-Y. , Niklasson G. A. , Granqvist C. G. 
Published: September 2011

ABSTRACTThermochromic materials have temperature-dependent optical properties. This paper discusses the limitations of thermochromic VO2 films for energy efficient fenestration and shows from calculations that nanocomposites containing VO2 can have superior properties and display high luminous transmittance and large temperature-dependent solar transmittance modulation. Even better results may be found for nanoparticles of VO2:Mg.
ZnO Thin Films of High Crystalline Quality Deposited on Sapphire and GaN Substrates by High Temperature Sputtering
Authors: Borysiewicz Michał A. , Pasternak Iwona , Dynowska Elżbieta , Jakieła Rafał , Wzorek Marek , Kolkovski Valery , Dużyńska Anna , Kamińska Eliana , Piotrowska Anna 
Published: September 2011

ABSTRACTSingle orientation ZnO (00.2) films were deposited by means of high temperature high vacuum reactive magnetron sputtering onto Al2O3 (0001) and GaN (0001) substrates. In order to obtain films of high crystalline quality a novel approach to ZnO sputter deposition was employed, adapting the practice used in MBE technology, of using a MgO buffer layer deposited on sapphire at a high-temperature followed by a ZnO nucleation layer deposited at low temperature. ZnO films were also grown on epitaxial GaN/Al2O3 substrates where the GaN layer was treated as the buffer layer. Following the deposition, all samples were annealed ex-situ in an O2 flow at 800°C. The obtained ZnO films have a lattice constant c equal to 5.2036 Å and 5.214 Å for the films deposited on Al2O3 and GaN substrates, respectively. Secondary ion mass spectroscopy depth profiles, scanning and transmission electron microscopy cross sectional images and atomic force microscope were used to characterize the structural properties of the films. Electrical properties were assessed using Hall effect measurement. Photoluminescence spectra were also taken.
Microstructure and Its Physicochemical Basis for the White Porcelain from Gongyi Kiln of Henan Province in China
Authors: Li Weidong , Luo Hongjie , Sun Xinmin , Liu Lanhua , Lu Xiaoke , Zhao Zhiwen , Guo Musen 
Published: September 2011

ABSTRACTGongyi is the birthplace and one of the most famous production areas of white porcelain in China. In this study, white porcelain samples from the Northern Wei to Tang Dynasties excavated from Baihe and Huangye kiln sites were analyzed to investigate microstructure and its physicochemical basis. The result demonstrates that the formation of an interaction layer of Anorthite crystals and the accompanied phase-separation structure at glaze-body boundary is a common character of microstructure. And there is little probability for crystal precipitation within the glaze layer.
A study on the importance of isolation of the active regions for high performance organic circuits
Authors: Myers R. , Donaghy D. , Raja M. 
Published: September 2011

ABSTRACTThe authors present electrical comparisons on an array of test structures including organic lateral diodes and thin film transistors (OTFT), fabricated with a range of disordered and polycrystalline organic semiconductors, to examine the increasing need for effective isolation for organic-based circuits. As the minimum feature size decreases, circuit components become closely positioned, which leads to increased electrical crosstalk. The organic semiconductors utilised for this work include solution-processable organic semiconductors such as disordered polymers P3HT and PTAA, and a polycrystalline material TIPS-pentacene. In order to predict the magnitude required for isolation for the different semiconductors, simple test structures have been designed consisting of two gold electrodes separated by a distance ranging from 4 μm up to 2000 μm. The bulk conductivity from such test structures provides the limits at which circuit components may be placed for crosstalk free operation. The work presented culminates in the development of an isolation layer to help reduce the off-currents and gate leakages of the OTFTs.
Comparison between the optical and surface properties of TiO2 and Ag/TiO2 thin films prepared by sol-gel process
Authors: Viana Marcelo M. , Mohallem Nelcy D. S. 
Published: September 2011

ABSTRACTColloidal precursor solutions, obtained from a mixture of titanium isopropoxide, isopropyl alcohol and silver nitrate, were used to fabricate amorphous TiO2 and Ag/TiO2 thin films by sol-gel process. The films were deposited on borosilicate substrates, which were heated at 400 °C for 30 minutes and cooled rapidly to the formation of amorphous coatings. The films were investigated by X-ray diffraction, scanning electron microscopy, atomic force microscopy and UV-vis spectroscopy. The thickness, roughness, refraction index, and particle size of the TiO2 and Ag/TiO2 films were determined and compared. Finally, hydrophobic-hydrophilic property was evaluated to the thin films produced.
(Green) Photocatalytic Synthesis Employing Nitroaromatic Compounds
Authors: Dillert Ralf , Hakki Amer , Bahnemann Detlef W. 
Published: September 2011

ABSTRACTThe combination of a solid photocatalyst (TiO2) and a co-catalyst (p-toluenesulfonic acid) has been successfully applied for the light-induced conversion of nitroarenes in O2-free ethanolic suspensions yielding substituted quinolines and tetrahydroquinolines, while in the presence of TiO2 loaded with a noble metal (Pt, Pd) N-alkylarylamines and N,N-dialkylarylamines were formed. Depending on the compounds that have been detected by GC–MS the reaction mecha-nism is discussed comprising the formation of anilines and ethanal by a photocatalytic reaction step and their subsequent thermal reactions to quinolines, tetrahydroquinolines, and N-alkylated anilines via a Schiff base as an intermediate product.
Structural, Electronic and Defect Properties of Cu2ZnSn(S,Se)4 Alloys
Authors: Chen Shiyou , Gong Xin-Gao , Walsh Aron , Wei Su-Huai 
Published: September 2011

ABSTRACTKesterite Cu2ZnSnS4 (CZTS) and Cu2ZnSnSe4 (CZTSe) compounds are candidate low-cost absorber materials for thin-film solar cells, and a light-to-electricity efficiency as high as ~10% has been achieved in the solar cell based on their alloys, Cu2ZnSn(S,Se)4 (CZTSSe). In this paper, we discuss the crystal and electronic structure of CZTSSe alloys with different composition, showing that the mixed-anion alloys keep the kesterite cation ordering, and are highly miscible with a small band gap bowing parameter. The phase stability of CZTS and CZTSe relative to secondary compounds such as ZnS and Cu2SnS3 has also been studied, showing that chemical potential control is important for growing high-quality crystals, and the coexistence of these secondary compounds is difficult to be excluded using X-ray diffraction technique. Both CZTS and CZTSe are self-doped to p-type by their intrinsic defects, and the acceptor level of the dominant CuZn antisite is deeper than Cu vacancy. Relatively speaking, CZTSe has shallower acceptor level and easier n-type doping than CZTS, which gives an explanation to the high efficiency of CZTSSe based solar cells.
Towards a Room Temperature Organic Spin Valve: Structural, Magnetic and Transport Properties of Fe3O4/PTCTE/Co Devices
Authors: Palosse Mathieu , Bedel-Pereira Elena , Olivié François , Séguy Isabelle , Villeneuve Christina , Blon Thomas , Gatel Christophe , Warot-Fonrose Bénédicte , Bobo Jean-François 
Published: September 2011

ABSTRACTThis paper describes first steps in preparation of an organic spin valve based on a perylene derivative (PTCTE) sandwiched between magnetite (Fe3O4) and cobalt (Co) ferromagnetic electrodes. MgO(001)/Fe3O4/PTCTE (450 nm)/Co devices were prepared with different Co soft deposition methods: off-axis dc-sputtering or Joule evaporation. Vibrating Sample Magnetometer (VSM) studies of the Fe3O4/PTCTE/Co stacks evidence spin valve behavior with magnetically uncoupled electrodes. These results are correlated with a morphological study by atomic force microscopy (AFM) of each layer and tunneling AFM (TUNA) for the investigation of inhomogeneity of current distribution in the devices. Finally, macroscopic I-V characteristics performed on the same devices will be presented and compared with TUNA results.
Growth and characterization of orientation patterned GaAs crystals for non-linear optical frequency conversion
Authors: Martínez O. , Avella M. , Hortelano V. , Jiménez J. , Snure M. , Lynch C. , Bliss D. 
Published: September 2011

ABSTRACTOrientation patterned (OP)-GaAs crystals have high potential as non linear optical systems. Mid-infrared and terahertz lasers sources can be fabricated with these crystals by frequency conversion from shorter wavelength sources. The optical propagation losses are critical; therefore, the OP-GaAs crystals must have high quality with low incorporation of defects and high homogeneity to reduce the refractive index fluctuations. Defects with electro-optic signature must be characterized in order to reduce their presence. Cathodoluminescence studies of these crystals permit the distribution of the main defects to be established, both extended and point defects. Special attention is paid to the role of the walls between the two domain orientations, and to the incorporation of impurities in Si-doped samples.
Preparation of luminescent inorganic core/shell-structured nanoparticles
Authors: Milde Moritz , Dembski Sofia , Rupp Sabine , Gellermann Carsten , Sextl Gerhard , Batentschuk Miroslaw , Osvet Andres , Winnacker Albrecht 
Published: September 2011

ABSTRACTSiO2 nanoparticles (NPs) were coated with Eu3+-doped calcium phosphate (CP) and Mn2+-doped ZnO to give Zn2SiO4 via a modified Pechini sol-gel process. Annealing at high temperatures resulted in NPs with an amorphous core and a crystalline luminescent shell. It was shown that this procedure can be applied to silica cores with diameters below 300 nm. By transmission electron microscopy, elemental analysis and from X-ray diffraction patterns it was determined that shell composition and structure are influenced by the annealing temperature and pH of the coating solution. Measurements of photoluminescence intensities displayed their dependency on the concentration of dopant in the resulting core/shell NPs.
Size-dependent Reactivity in the Functionalization of Nanostructured Silicon Surfaces
Authors: Kelly Joel A. , Shukaliak Amber M. , Fleischauer Michael D. , Veinot Jonathan G.C. 
Published: September 2011

ABSTRACTThe reactivity of silicon nanocrystals (Si-NCs) in near-UV photochemical hydrosilylation was evaluated as a function of size. Results show that Si-NCs with photoluminescence (PL) in the visible spectral region react faster than Si-NCs with near-IR PL. Fourier-transform infrared (FTIR) spectroscopy suggests this difference in reactivity is due to quantum size effects in the exciton-mediated mechanism proposed for this reaction. We have carried out a detailed comparison of Si-NC reactivity in photochemical and thermal hydrosilylation and determined the conditions under which Si-NCs may be size-selected based on their reactivity.
Non-lithographic Patterning of Oxide-Embedded Silicon Nanoparticles
Authors: Rodríguez Núñez José R. , Johnson Melanie , Veinot Jonathan G. C. 
Published: September 2011

ABSTRACTOxide-embedded Silicon nanoparticles (OE-Si-NPs) are of great interest for many applications due to unique size effects observed when their size drops below 5 nm (Silicon’s Bohr exciton radius). Some of the suggested applications require patterning of the nanoparticles in an ordered array. Lithographic methods to pattern Si-NPs are common in the literature, however these methods can be costly, and are not time-efficient. Recently, non-lithographic patterning techniques have become very attractive because they are cost-effective and straightforward. In this proceeding we will demonstrate non-lithographic patterning of OE-Si-NPs characterized via AFM and XPS.
An Evaluation of Decorative Techniques on a Red-Figure Attic Vase from the Worcester Art Museum using Reflectance Transformation Imaging (RTI) and Confocal Microscopy with a Special Focus on the “Relief Line”
Authors: Artal-Isbrand Paula , Klausmeyer Philip , Murray Winifred 
Published: September 2011

ABSTRACTDecorative features on a Greek red-figure stamnos in the collection of the Worcester Art Museum were examined using Reflectance Transformation Imaging (RTI) and scanning laser confocal microscopy. These two surface examination tools helped to answer questions relating to the decorative process, particularly the tools and techniques that Attic painters used to create the so-called glossy black “relief lines” and “relief dots.” This research also incorporated fabricated mock-ups to help understand the ancient technology. It was determined that the relief line was not produced by an extruded method, but with a brush made of one or very few hairs, an idea first proposed by Gérard Seiterle in 1976 and termed Linierhaar. It was observed that not one but two distinct types of relief lines exist: the “laid” line (proposed by Seiterle) characterized by a ridge running through the middle of the line and the “pulled” line (proposed in this paper) which has a furrowed profile. Both line types were reproduced with a Linierhaar. Additionally, relief dots were replicated using a conventional brush. Surface examinations of other red-figure vessels using RTI and the confocal microscope suggest these conclusions apply to vessels of this genre as a whole.
Structural Degradation of Third Millennium B.C.E. Archaeological Wood from Shahr-i Sukhta, Iran
Authors: Mohammadi Achachluei Mohsen , Vatankhah Gholamreza 
Published: September 2011

AbstractDetection of structural changes has a great importance in conservation and treatment of wooden artifacts found in burial environments. In this study, two wooden samples excavated in Shahr-i Sukhta, an important prehistoric site in eastern Persia, were tested by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). FTIR results showed that decay of lignin occurred. This was accompanied by cellulose degradation. SEM images showed detachment of wood fibers in cross sections and cell wall breakage in tangential sections of the wood samples. These results indicated that the structural change in cellulose and lignin has caused detachment of wood fibers and cell wall breaking. This is the sign of low physical characteristics of wood which has direct relevance to cellulose decay and lignin degradation in middle lamella of wood cells. Cellulose chain breaking over time, has produced stresses in the compound middle lamella layer of the cell wall, that became accelerated in the middle of the lamella layer. Consequently, wood fibers were detached, and disintegration and powdering of wood surfaces occurred.
New Dynamic Air-Brush Technique for SWCNTs Deposition: Application to Fabrication of CNTFETs for Electronics and Gas Sensing
Authors: Bondavalli P. , Gorintin L. , Legagneux P. , Simonato J.P. , Cailler L. 
Published: September 2011

ABSTRACTThis contribution deals with Carbon Nanotubes Field Effect transistors (CNTFETs) based gas sensors fabricated using a completely new dynamic spray based technique (patented) for SWCNTs deposition. The extreme novelty is that our technique is compatible with large surfaces, flexible substrates and allows to fabricate high performances transistors exploiting the percolation effect of the SWCNTs networks achieved with extremely reproducible characteristics. Recently, we have been able to achieve extremely selective measurement of NO2, NH3 and CO using four CNTFETS fabricated using different metals as electrodes, exploiting the specific interaction between gas and metal/SWCNT junctions. In this way we have identify an electronic fingerprinting of the gas detected. The response time is evaluated at less than 30sec.
Fracture mechanism of copper micro-crystals by diamond single crystal
Authors: Kano Seisuke , Korenaga Atsushi 
Published: September 2011

ABSTRACTCopper micro-crystal fracture mechanisms were discussed with the machining precisions under the several cutting conditions, such as cutting speed, cutting depth and width of grove formation by the diamond single crystal cutting tool which the scoop face of (100) crystal face. For the cutting test, the copper single at the size of 10 mm in diameter and 5 mm in height as the test piece which cut by single crystal diamond cutting tool with silicon oil on the shaper type ultra-precision cutting machine. Before groves cutting, the specimen surface was cut as flat by cutting-off tool (corner diameter; 50 mm, cutting width; 3.0 mm, scooping angle; 0 degree, and escape angle; 7.0 degree) at the work speed as 4000 mm/min and cutting depth of 5 μm. For the V-shape grove cutting, the flat copper surface was cut with the diamond-point cutting tool (V angle = 90 degree, scooping angle = 0 degree, and escape angle = 7.0 degree) at the work speed as 4-4000 m m/min and cutting depth of 0.1-10 μm for finishing machining. The cut machined surface was observed by optical microscope comparing the grove shapes. The diamond-point tool was also observed by optical microscope. As results of the cutting test of copper single crystal, the machining precision was better for the crystallographic direction of $[01\bar 1]$ than the direction of $[00\bar 1]$ under the deeper cutting profiles. The mechanisms of this fracture results considered that the slip plane of (111). On the other hand, shallow grove under 1.0 μm was better tracks scratched for the crystallographic direction of $[00\bar 1]$ than the direction of $[01\bar 1]$. This result was also considered that the slip plane related to the fracture behavior. For copper crystal cutting in nanometric scale, the crystallographic direction was quite important.
Impact of a Finite Shunt Resistance on the Dark Spectral Response of a-Si:H/μc-Si Thin-film Multi-junction Photovoltaic Devices
Authors: Pravettoni Mauro , Virtuani Alessandro 
Published: September 2011

ABSTRACTHydrogenated amorphous silicon (a-Si:H) multi-junction devices have demonstrated a way to increase the efficiency of a-Si:H thin-film photovoltaic (PV) modules, which is now well above 10%. Since the current–matching behaviour of all sub-cells is a critical aspect, the measurement of the spectral response (SR) of all junctions provides valuable information to optimize the device performance under a given spectral distribution. In this work the authors investigate the impact of low shunt resistances on the SR of a double-junction a-Si:H/μc-Si PV module. The origin of a low shunt resistance in a-Si:H multi-junction devices is revised. A simple theoretical approach is then used to describe the anomalous dark SR observed experimentally as a consequence of the presence of low shunt resistances. The dark SR allows therefore to detect the presence of shunts and discriminate the defective sub-cell.
Characterization of Green Laser Crystallized GeSi Thin Films
Authors: Rangarajan Balaji , Brunets Ihor , Oesterlin Peter , Kovalgin Alexey Y. , Schmitz Jurriaan 
Published: September 2011

ABSTRACTGreen laser crystallization of a-Ge0.85Si0.15 films deposited using Low Pressure Chemical Vapour Deposition is studied. Large grains of 8x2 μm2 size were formed using a location-controlled approach. Characterization is done using Scanning Electron Microscopy, Atomic Force Microscopy, X-Ray Photoelectron Spectroscopy and X-Ray Diffraction.
Hopping transport in doped co-deposited mixed-phase hydrogenated amorphous/nanocrystalline silicon thin films
Authors: Wienkes L. R. , Blackwell C. , Kakalios J. 
Published: September 2011

ABSTRACTStudies of the electronic transport properties of n-type doped hydrogenated amorphous/nanocrystalline silicon (a/nc-Si:H) films deposited in a dual-plasma co-deposition reactor are described. For these doped a/nc-Si:H, the conductivity increases monotonically for increasing crystal fractions up to 60% and displays marked deviations from a simple thermally activated temperature dependence. Analysis of the temperature dependence of the activation energy for these films finds that the dark conductivity is best described by a power-law temperature dependence, σ = σo (T/To)n where n = 1 – 4, suggesting multiphonon hopping as the main transport mechanism. These results suggest that electronic transport in mixed-phase films occurs through the a-Si:H matrix at lower nanocrystal concentrations and shifts to hopping conduction between clusters of nanocrystals at higher nanocrystal densities.
Reflectance Improvement by Thermal Annealing of Sputtered Ag/ZnO Back Reflectors in a-Si:H Thin Film Silicon Solar Cells
Authors: Söderström Karin , Haug Franz-Josef , Pahud Céline , Biron Rémi , Escarré Jordi , Duchamp Martial , Dunin-Borkowski Rafal , Ballif Christophe 
Published: September 2011

ABSTRACTSilver can be used as the back contact and reflector in thin film silicon solar cells. When deposited on textured substrates, silver films often exhibit reduced reflectance due to absorption losses by the excitation of surface plasmon resonances. We show that thermal annealing of the silver back reflector increases its reflectance drastically. The process is performed at low temperature (150°C) to allow the use of plastic sheets such as polyethylene naphthalate and increases the efficiency of single junction amorphous solar cells dramatically. We present the best result obtained on a flexible substrate: a cell with 9.9% initial efficiency and 15.82 mA/cm2 in short circuit current is realized in n-i-p configuration.