bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hybrid Inorganic/Organic Self-Assembled Clays Nanocomposites for Roll to Roll Fabrication in Photovoltaics
Authors: Kariuki Peter Njagwa , Gendron Jessica , Madl Christopher Matthew , Chiguma Jasper , Hagerman Michael E , Borgesen Peter , Jones Wayne E 
Published: August 2010

AbstractWe have been developing a new approach to layered hybrid (inorganic/organic) photovoltaic materials for fabrication by Roll-to-Roll (R2R) manufacturing. In this report, we combine the low cost and processability of organic electrically conducting polymers with the efficiency of dye sensitized titanium dioxide, semi-conductor quantum dots (CdSe) self-assembled on layered clay materials (Laponite) onto indium tin oxide coated flexible substrate polyethylene terephthalate (PET) substrates. We have shown electron transfer, guest-guest and host-guest interactions, charge separation, spectral line broadening, and quenching of fluorescence signals which indicate electronic coupling of the dye [Ru(bpy)3]2+ on a CdSe nanocrystal and titanium dioxide nanoparticles. Scanning electron microscopy and atomic force microscopy demonstrate successful nanoparticle formation and thin film self-assembly, as well as surface morphology and polymer thickness.
Light Effective Mass in the Widely-Dispersed Valence Band of Single Crystalline Rubrene Observed by High-Resolution Angle-Resolved Ultraviolet Photoelectron Spectroscopy
Authors: Nakayama Yasuo , Machida Shin-ichi , Duhm Steffen , Xin Qian , Funakoshi Akihiro , Ogawa Naoki , Kera Satoshi , Ueno Nobuo , Noguchi Yutaka , Ishii Hisao 
Published: August 2010

AbstractHigh-resolution angle resolved ultraviolet photoelectron spectroscopy measurements were conducted on rubrene single crystals successfully through relief of the sample charging assisted by a laser illumination. Significant dispersion of the valence band was clearly resolved. The band width W and the hole effective mass mh* were estimated to be 0.4 eV and 0.7m0, respectively, along the most conductive direction. The present results strongly suggest that the transport nature in rubrene single crystals should be described in the band transport framework of a delocalized charge carrier.
Effects of LSCO Buffer Layer on the Microstructure and Dielectric Properties of Ba0.6Sr0.4TiO3 Films Prepared by Sol-gel Methods
Authors: Han Songwei , Yu Shengwen , Cheng Jinrong 
Published: August 2010

AbstractIn this work, Ba0.6Sr0.4TiO3(BST) thin films were deposited on Ti substrates using conductive La0.5Sr0.5CoO3 (LCSO) as buffer layers. Both BST and LSCO films were prepared by sol-gel methods. The structure and morphology of BST and LSCO films were analyzed by X-ray diffraction (XRD). XRD results show that both BST and LSCO films have perovskite structure with random orientation. The dielectric properties of BST films were dependent on the thickness of LSCO buffer layers. Upon using LSCO buffer layers, the dielectric properties of BST films were significantly improved. The dielectric constant, tunability, and dielectric loss of BST thin films for LSCO of 150 nm achieved about 453, 0.032 and 31.26% respectively.
Investigation of the Pb Depletion in Single and Dual Pulsed Laser Deposited Epitaxial PZT Thin Films and Their Structural Characterization
Authors: Mukherjee Devajyoti , Hyde Robert H , Dhakal Tara , Srikanth Hariharan , Mukherjee Pritish , Witanachchi Sarath 
Published: August 2010

AbstractWe have investigated the Pb depletion in laser ablated PZT (PbZr0.52Ti0.48O3) films through a systematic study of PZT target-laser interactions for both single laser and dual-laser ablation methods. The study includes films deposited from a stoichiometric and an excess PbO PZT targets. The films were deposited on single crystal SrTiO3[100] substrates at 550˚C with a background oxygen pressure of 500 mT. Single laser deposited films at a laser fluence of 5J/cm2 produced the highest Pb content while dual-laser ablated films where an excimer and a CO2 pulsed lasers were synchronized for ablation produced high Pb content for an excimer laser fluence of less than 2J/cm2. This enabled the growth of particulate-free PZT films with high Pb content. ICCD imaging of the plasma plumes showed variations in the expansion profiles at different laser fluencies that correlated well with the Pb content observed in the deposited films.
Enhancement in Ferroelectricity in V-Doped ZnO Thin Film Grown using Laser Ablation
Authors: Dhakal Tara , Mukherjee Devajyoti , Hyde Robert H , Srikanth Hariharan , Mukherjee Pritish , Witanachchi Sarath 
Published: August 2010

AbstractWe report evidence of enhancement in ferroelectricity in thin films of vanadium (V) doped ZnO grown at higher oxygen pressure. This process reduces oxygen deficiency and the material becomes very insulating, which in turn lowers the leakage current through the ferroelectric capacitor. 2 at. % V doped ZnO films, with thickness of approximately 1 μm were grown epitaxially on c-cut sapphire (Al2O3) (0001) at a growth temperature of 600°C. X-ray analysis showed the layers to be epitaxial where the (0002) diffraction peak had a rocking curve FWHM below 1°. The films with higher oxygen pressure were more insulating than the one grown with lower oxygen pressure. The saturation polarization doubled when the growth pressure increased from 300 mT to 500 mT. Time gated ICCD imaging of the ablated plasma during various O2 pressures and how it translated to the film quality are presented.
Low Temperature Fabrication of Sol-Gel Derived Dielectric (Ba,Sr)TiO3 Thin Films
Authors: Sakurai Hideaki , Watanabe Toshiaki , Soyama Nobuyuki 
Published: August 2010

AbstractWe studied the nucleation and crystallization of sol-gel derived (Ba0.7Sr0.3)TiO3 [BST(70/30)] thin films at low temperatures between 500 to 600°C on Pt(111)/TiO2/SiO2/Si substrates by a process using a combination of 2-ethyl-hexanoate based solutions and modified film preparation. We found that BST films could be crystallized at 500°C and that the films obtained had a columnar-like grainy microstructure with favorable electrical characteristic such as high relative permittivity (ɛr) of 310 at 10 kHz and high tunability of 51% at a bias electric field of 250 kV/cm. Moreover, we investigated annealing temperature dependence of BST(70/30) thin films. The results indicated er and tunability increased with annealing temperature up to 450 and 58%, respectively.
Towards a High Quality Factor DC Electric Field Switchable Barium Strontium Titanate Solidly Mounted Resonator
Authors: Saddik George N. , Son Junwoo , Stemmer Susanne , York Robert A. 
Published: August 2010

AbstractBarium strontium titanate solidly mounted resonators (SMR) were fabricated with three different acoustic Bragg reflectors (ABR) on a sapphire substrate. The three devices had ABR structures consisting of W/SiO2/W/SiO2, Mo/SiO2/Mo/SiO2, and Pt/SiO2/Pt/SiO2respectively. The s-parameters of all three devices were measured. The results showed that the quality factor increased as a function of the material in the ABR structure. The quality factor for the devices with tungsten, molybdenum and platinum in the ABR structures are 101, 88, and 31, respectively. This investigation showed how the material in the ABR structure can contribute to the acoustic loss in the device.
Field-induced phase transition and its impact on the magnetoelectric effect in P(VDF-HFP)/Metglas laminates
Authors: Lu David Sheng-Guo , Zhou Xin , Fang Zhao , Zhang Qiming 
Published: August 2010

AbstractThe field-induced phase transition driven by electric field was observed in poly(vinylidene fluoride – hexafluoropropylene) (P(VDF-HFP)) 90/10 wt% copolymers. Experimental results indicated that the electric field may remarkably affect the remanent polarization in terms of changing the D-E loop forms from double loops to single loop, starting from 68 MV/m, and completing at 216 MV/m. It was found that the remanent polarization as well as the piezoelectric constant d31 had a linear relationship with the poling electric field in above electric field range. Thus the magnetoelectric (ME) coupling coefficient ME in P(VDF-HFP)/Metglas laminates increased with the poling electric field. Moreover, the cyclic poled ME device demonstrated different peak d.c. magnetic bias field HDC on the ME - HDC curves from conventional room temperature poled ones. The peak ME coefficient obtained was 4 V/cm Oe.
Finite-Electric Field Study of Pressure Effects on Polarization Rotation in PbTiO3
Authors: Ganesh Panchapakesan , Cohen Ronald 
Published: August 2010

AbstractWe perform first-principles finite-electric field simulations of PbTiO3 both at zero and high pressures to investigate the effect of pressure on polarization rotation. We find that whereas a large electric field is required at zero pressure to induce a phase transition from the tetragonal (P4mm) phase to the rhombohedral (R3m) phase, at 8GPa a relatively small electric field is required indicating the greater ease of polarization rotation at high pressure. Pressure reduces the relative well depth between the two phases leading to a softer free-energy surface. This explains the increased electro-mechanical coupling obtained in PbTiO3 with pressure.
Finite-temperature Anisotropic Elastic Properties of Ni-Mn-In Magnetic Shape Memory Alloy
Authors: Williams Kristen Smith , Cagin Tahir 
Published: August 2010

AbstractDesigning magnetic shape memory materials with practicable engineering applications requires a thorough understanding of their electronic, magnetic, and mechanical properties. Experimental and computational studies on such materials provide differing perspectives on the same problems, with theoretical approaches offering fundamental insight into complex experimental phenomena. Many recent computational approaches have focused on first-principles calculations, all of which have been successful in reproducing ground-state structures and properties such as lattice parameters, magnetic moments, electronic density of states, and phonon dispersion curves. With all of these successes, however, such methods fail to include the effects of finite temperatures, effects which are critical in understanding how these properties couple to the experimentally-observed martensitic transformation. To this end, we apply the quasi-harmonic theory of lattice dynamics to predict the finite-temperature mechanical properties of Ni-Mn-In magnetic shape memory alloy. We employ first-principles calculations in which we include vibrational contributions to the free energy. By constructing a free energy surface in volume/temperature space, we are able to evaluate key thermodynamic properties such as entropy, enthalpy, and specific heat. We further report the elastic constants for the austenite and martensite phases and evaluate their role as a driving force for martensitic transformation.
Hydrogen Passivation of Defects in Crystalline Silicon Solar Cells
Authors: Stavola Michael , Jiang Fan , Kleekajai Suppawan , Wen Lanlin , Peng Chao , Yelundur Vijay , Rohatgi Ajeet , Hahn Giso , Carnel Lode , Kalejs Juris 
Published: August 2010

AbstractHydrogen is commonly introduced into silicon solar cells to reduce the deleterious effects of defects and to increase cell efficiency. We have developed strategies by which hydrogen in silicon can be detected by IR spectroscopy with high sensitivity. The introduction of hydrogen into Si by the post-deposition annealing of a hydrogen-rich, SiNx coating has been investigated to determine hydrogen's concentration and penetration depth. Different hydrogenation processes were studied so that their effectiveness for the passivation of bulk defects could be compared. The best conditions investigated in our experiments yielded a hydrogen concentration near 1015 cm-3 and a diffusion depth consistent with the diffusivity of H found by Van Wieringen and Warmoltz.
Incorporation of Na in Low-Temperature Deposition of CIGS Flexible Solar Cells
Authors: Zachmann Hendrik , Puttnins Stefan , Daume Felix , Rahm Andreas , Otte Karsten , Caballero Raquel , Kaufmann Christian A. , Eisenbarth Tobias , Schock H.W. 
Published: August 2010

AbstractDifferent methods for Na incorporation are known for the use of Na-free substrates like stainless steel or polyimide foil. In this work Cu(In,Ga)Se2 (CIGS) absorber layers with different amounts of Na are investigated. The CIGS samples were prepared via a roll-to-roll deposition process with ion beam assistance (Solarion) and by a multi-stage low temperature co-evaporation process (HZB). Na was either incorporated via in-situ co-evaporation of NaF (for roll-to-roll deposition) or by a Na-containing precursor (for multi-stage deposition).
With increasing amounts of Na an increase of VOC is observed for both deposition tech-niques. In contrast, within the deposition parameters used, jSC decreases with increasing Na amount for co-evaporation of NaF while it seems unaffected when using a NaF precursor layer. The elemental depth profiles of the different CIGS thin films were studied via secondary ion mass spectroscopy and were found to depend strongly on the deposition technique.
It seems that beneficial effects of the addition of Na are independent of the method of in-corporation, even if the distribution of Na in the CIGS layer is different due to different methods of incorporation and CIGS deposition processes.
High Efficiency Copper Indium Gallium DiSelenide (CIGS) by High Power Impulse Magnetron Sputtering (HIPIMS): A Promising and Scalable Application in Thin-film Photovoltaics
Authors: Halbe Ankush , Johnson Paul , Jackson Shen , Weiss Robert , Avachat Upendra , Welsh Alex , Ehiasarian Arutiun P. 
Published: August 2010

AbstractA novel method to deposit Copper Indium Gallium Diselenide (CIGS) using High Power Impulse Magnetron Sputtering (HIPIMS) was demonstrated and compared to the existing DC magnetron sputtering process. The metal-ion assisted thin-film growth inherent to a HIPIMS deposition process was used to advantage in depositing CIGS films. The HIPIMS plasma was characterized by measuring ion currents on a Langmuir probe placed into the plasma sufficiently close to the substrate. The high density plasma consisting of both metal and metal ions resulted in CIGS thin-film solar cells of superior conversion efficiencies (˜13%) as compared to conventional DC magnetron sputtering (˜10%). The efficiency enhancement was attributed to the improvement in the shunt resistance of the solar cell which corresponds to the increase in the density of the CIGS layer. Furthermore, it was also possible to grow large grained CIGS (˜1 micron) with high mobility metal-ions from the HIPIMS process.
The scalability potential of the HIPIMS CIGS process was also demonstrated by running a 1.5 m long Copper-Indium-Gallium rotatable in a selenium environment using a HIPIMS power supply. The cylindrical magnetron was run at an average power of 7.8 KW and peak powers of as much as 300 KW with controlled arcing. The existence of a HIPIMS plasma was confirmed by the ion currents on the Langmuir probe and the metal signals from a Plasma Emission Monitor (PEM).
Intrinsic Degradation in Alq3-Based OLEDs Probed by Deep-Level Optical Spectroscopy
Authors: Nakano Yoshitaka 
Published: August 2010

AbstractWe have successfully investigated degradation-induced variations in electronic band-gap states in the emissive region of the Alq3-based OLEDs by a deep-level optical spectroscopy technique. Through the intrinsic degradation, both deep-level traps and near-band-edge transitions in the Alq3 emissive zone are found to be red-shifted significantly towards their corresponding bulk levels of the Alq3 single layer. These variations in the interfacial electronic states are probably induced by the intrinsic degradation and indicate that initial molecular structures characteristic of the Alq3 emissive zone are transformed into the bulk-like relaxed ones through the degradation.
Direct Study of the Thermal Conductivity in Aluminum Nanowires
Authors: Stojanovic Nenad , Maithripala D.H.S. , Berg Jordan M. , Holtz Mark 
Published: August 2010

AbstractThermal conductivity and electrical resistivity of 1 μm long aluminum nanowires, 75, 100, and 150nm in width and 100nm thick, were measured at room temperature. The method consists of microfabricated electrothermal test devices and a model-based data processing approach using finite-element analysis (FEA). The electrical and thermal properties of the nanowires differ significantly from bulk values while electrical resistivity agrees well with theoretical prediction. Electron transport equation models, which adequately describe the resistivity data, consistently underestimate the thermal conductivity. Incorporating a phonon contribution of ˜ 21 W/m·K to the total thermal conductivity is found to accurately describe the measured values.
Temperature Dependence of Nanoscale Friction Investigated with Thermal AFM Probes
Authors: Greiner Christian , Felts Jonathan R. , Dai Zhenting , King William P. , Carpick Robert W. 
Published: August 2010

AbstractMeasurements of nanoscale friction between silicon AFM tips featuring an in-situ solid state heater and silicon substrates (both with native oxide) were performed. The temperature of the heater was varied between room temperature and approximately 650 °C. For these temperatures and the silicon substrate, the temperatures at the point of contact are estimated to range from room temperature to approximately 120±20 °C. Experiments were carried out in ambient atmosphere (˜30% relative humidity) and under dry nitrogen. Tests under constant load revealed that in the presence of ambient, friction increased with heater temperature whereas it did not change in dry nitrogen. For experiments carried out for different tip velocities (40 to 7800 nm/s), friction decreased with velocity in ambient and did not change in dry nitrogen. Both trends can be explained by thermally-assisted formation of capillary bridges between tip and substrate and the kinetics of capillary condensation under ambient conditions.
Ultrafast Defect Manipulation with Optical Anisotropy in Fused Silica
Authors: Shimotsuma Yasuhiko , Sakakura Masaaki , Kazansky Peter G. , Miura Kiyotaka , Hirao Kazuyuki 
Published: August 2010

AbstractWe report the evidence that the oxygen defects induced by focusing an intense infrared femtosecond laser pulse in fused silica can be self-organized by the interference pattern between photon and electron plasma wave. Self-organized nanostructure with a sub-wavelength modulation in refractive index exhibits form birefringence which is rewritable and directionally-controllable. Intriguingly, such optical anisotropy, which indicates a remarkable non-reciprocity, has initially evolved from residual birefringence originated from internal stress distribution due to local heating followed by structural change, regardless of interpulse time. This anisotropic light-matter interaction could be interpreted in terms of an asymmetric relation between light polarization and pulse front tilt. Apart from fundamental understanding of self-organization mechanism, the direction of encoded birefringence can introduce an entirely new concept for rewritable optical storage beyond the diffraction limit of light.
Osteoconductive HAp and TiO2Coatings on Titanium using Hydro-process
Authors: Yamamoto Dai , Kuroda Kensuke , Ichino Ryoichi , Okido Masazumi 
Published: August 2010

AbstractHydroxyapatite (Ca10(PO4)6(OH)2, HAp) and titanium dioxide (TiO2, titania) are of interest for bone-interfacing implant applications, because of their demonstrated osteoconductive properties. They were coated on the titanium implants using hydro-processes and investigated thein vivoperformance. HAp coatings were formed on cp-titanium plates or rods by the thermal substrate method in an aqueous solution included 0.3 mM Ca(H2PO4)2and 0.7 mM CaCl2. In the formation of carbonate apatite coating, CaHCO3was added to the solution, and in HAp/gelatin and HAp/collagen composite coatings, acid-soluble collagen (Type I) was added. The coating experiments were conducted at 313-433 K and pH = 8 for 15 or 30 min. Titania films were formed on the titanium implants by anodizing at < 100 V in 0.1 M H2SO4, H3PO4, and NaOH aqueous solutions at 298 K. The properties for the coated samples were studied using XRD, EDX, FT-IR, and SEM. And the surface roughness of titania coatings was measured. In in vivo evaluations, the coated rod specimens were implanted in rats femoral for 2 weeks, the osteoconduction on them was evaluated. Two weeks postimplantation, new bone formed on the coated and non-coated titanium rods in the cancellous bone and cortical bone, respectively. Bone-implant contact ratio, RB-I, which was used for the evaluation of new bone formation, was significantly depended on the compound formed on titanium implants, and also the coating processes.
Modified Nanodiamonds for Adsorption of Propidium Iodide and Aflatoxin
Authors: Gibson Natalie , Luo Tizy-Jiun Mark , Shenderova Olga , Choi Yong-Jae , Brenner Donald W 
Published: August 2010

AbstractNanodiamonds (NDs) have desirable chemical, physical and biological properties that lend them to a wide range of applications. ND’s facile surface chemistry, for example, can be used to create a high affinity for adsorbing various biological molecules. However, NDs, which are commercially available from multiple vendors, show inconsistencies with surface groups, aggregate sizes and impurity contents that may limit adsorption. We explore adsorption mechanisms of molecules to NDs in efforts to expand ND applications to drug delivery agents, bio-labels and enterosorbents. In doing so, several types of NDs and modification methods are evaluated to increase adsorption capacity and selectivity of propidium iodide and aflatoxin B1. Capacities and binding strengths of target molecules are assessed by Langmuir isotherms and transform calculations. UV-Vis spectroscopy shows our modification treatments are successful in increasing ND adsorption capacities. Additionally, cyclic voltammetry measurements, used to monitor in-situ adsorption, show electrochemical detection even after binding.
Microscale Structural Model of Alzheimer's Aβ(1-40) Amyloid Fibril: Comparative Study of 2- and 3-fold Morphologies
Authors: Paparcone Raffaella , Buehler Markus J 
Published: August 2010

AbstractAmyloid fibrils aggregation is a key pathological feature of many severe degenerative disorders including Alzheimer’s disease and clinical dementia. Moreover, amyloids have been classified as intriguing molecules due to their exceptional strength, sturdiness and elasticity. However, physical models that explain the structural basis of these properties remain largely elusive, preventing the description of the link between their hierarchical structure and physical properties. Here we present an atomistic-based multiscale analysis based on computational materiomics, utilized to predict the structure of the two known polymorphous Alzheimer’s Aβ(1–40) amyloid fibers. We report an analysis of the energies, structural changes and H-bonding for varying amyloid fibril lengths, elucidating their size dependent properties. We also propose an explanation for the different stability of the two morphologies. A structural model of amyloid fibers with lengths of hundreds of nanometers at atomistic resolution is obtained. It predicts the formation of twisted amyloid microfibers in close agreement with experimental results. The approach used here provides a link between the fibril geometry, the chemical interactions and the most stable configuration, and resolves the issue of missing atomistic structures for long amyloid fibers.