bluuebunny/crossref_metadata_2025_split huggingface dataset:
Role of Rare-Earth Element Doping in the Cycleability of LiMn2O4 Cathodes for Li-ion Rechargeable Batteries
Authors: Singhal Rahul , Tomar Maharaj S , Oviedo Osbert , Das Suprem R , Katiyar Ram S 
Published: April 2011

AbstractWe have synthesized spinel LiMn1.99Nd0.01O4 and LiMn1.99Ce0.01O4 powder by chemical synthesis method. The synthesized powders were used to prepare cathodes for Li ion coin cells. The structural and electrochemical properties were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry and charge-discharge studies, respectively. The cyclic voltammetry of the cathodes revealed the reversible nature of Li-ion intercalation in the cell. The charge-discharge characteristics for LiMn1.99Ce0.01O4 were obtained in 3.5 V – 4.8 V voltage range, while for LiMn1.99Nd0.01O4 the charge-discharge were carried out in 3.4 V – 4.4 V range. The initial discharge capacities of LiMn1.99Ce0.01O4 and LiMn1.99Nd0.01O4 were obtained as 134mAh/g and 149 mAh/g, respectively. The coin cells were tested for up to 25 charge-discharge cycles and after 25 cycles the discharge capacities were determined to 79.5 mAh/g and 132 mAh/g for LiMn1.99Ce0.01O4 and LiMn1.99Nd0.01O4 cathodes respectively. However, by doping with a small concentration of rare earth materials, like Ce and Nd reduces the capacity fading in pure LiMn2O4 cathodes making it suitable for Li-ion battery applications.
Preparation and Characterization of Li4/3Ti5/3O4 Thin Films by Sol-gel Method
Authors: Hu C. , Zhang W. , Hao H. , Cao M. H. , Lai S. J. , Zhu X. J. , Liu H. X. 
Published: April 2011

AbstractIn the study Li4/3Ti5/3O4 thin films were deposited on Pt substrates by sol-gel method using a spin coator. The coated films are dried at 310-360 °C, and then annealed at 500-800 °C for 30min. The prepared films were characterized by X-ray diffraction, atomic force microscope and scanning electron microscope. The results indicated that the prepared film belonged to a spinel structure and had a uniform morphology. Electrochemical properties of the prepared electrode films were evaluated by using a discharge and charge test. From these results, it can be showed that the thin film electrode annealed at 700 °C exhibited good crystallinity, smooth surface morphology, high capacity, and good rechargeability. Therefore, This film was therefore suitable for use as an anode for thin-film microbatteries.
Enabling Aspects of Metal Halide Nanocomposites for Reversible Energy Storage
Authors: Badway Fadwa , Mansour Azzam , Plitz Irene , Pereira Nathalie , Weinstein Larry , Yourey William , Amatucci Glenn G 
Published: April 2011

AbstractThe concept of reversible and non reversible conversion in high bandgap metal fluorides is expanded through the introduction of mixed conducting matrices to form dense nanocomposite structures capable of good transport to nanodomains of metal fluorides. Specific examples for BiF3 and especially CuF2 using matrices of nominal composition of MoO3 are discussed. The reversible conversion mechanism of the metal halides is expanded to enable a new concept of electrochemically self assembled microbatteries (ESAMs) based on alkali halides. Such technology enables the fabrication of a solid state microbattery between two current collectors of various configurations on the microscale. First examples demonstrated based on LiI have demonstrated cell formation, appreciable energy density, and preliminary reversibility.
Materials and Design Study for Micromachined Solid Oxide Fuel Cells Membranes
Authors: Rey-Mermet Samuel , Muralt Paul 
Published: April 2011

AbstractMiniature solid oxide fuel cells (μSOFC) are very promising energy sources for portable devices. In this work we report on fabrication and on first experimental results of μSOFCs processed by means of silicon and thin film technology. All the layers involved in the PEN (Positive electrode-Electrolyte-Negative electrode) structure were sputter deposited on silicon wafer. The PEN membrane was liberated using deep silicon dry etching. The cathode is a combination of a very fine platinum grid covered by a thin LSC layer. The electrolyte is a bilayer of YSZ and CGO ionic conductors. Scanning electrons microscope and X-ray analysis show that the deposited films are polycrystalline with a columnar microstructure. The conductivities of these films are sufficiently high for cell operation at 550°C. The anode is composed of a NiO-Ni-CGO composite. A supporting structure consisting of an electroplated nickel grid is deposited on top of the anode and is part of it. The final PEN is a free standing 1 micron thick membrane, with a diameter of 5 mm. First measurements showed that this structure is mechanically stable up to 550°C and that the cell works with an OCV of 200 mV.
Low Temperature Synthesis and Electrochemical Properties of M0.8Sr0.2Co1-xFexO3(M = Ba, La, Pr) Nanoparticles: Effect of Grain Size on Lattice Symmetry
Authors: Magnone Enrico , Miyayama Masaru , Traversa Enrico 
Published: April 2011

AbstractThis study was performed to investigate the effect of grain size on crystallographic structure and electrochemistry properties for nanocrystalline La0.8Sr0.2Co1-xFexO3(x = 0.1 and 0.9) powders, as a suitable model for SOFC cathodes. Different sets of perovskite-type mixed oxides were successfully prepared by the amorphous citrate method. A particle size dependent modification in the lattice parameters of La0.8Sr0.2Co1-xFexO3 nanocrystalline powders was observed. Clear correlations between crystal size, oxygen content, crystallographic structure, and electrochemical performance were observed
Electrochemical Features of Li-Ni-Mn-Co Oxides
Authors: Adbel-Ghany Ashraf , Zaghib Karim , Mauger Alain , Gendron François , Eid A.E. , Abbas H. , Hashem Ahmed M , Ramana Chintalapalle V , Julien Christian M 
Published: April 2011

ABSTRACTWe report the electrochemical behavior of various layered oxides in Li cells. A series of LiNiyMnyCozO2 materials (with z=1-2y) was synthesized by “chimie douce” and investigated as positive electrodes in rechargeable lithium batteries. Electrochemical performances of LiNiyMnyCozO2 oxides are tested cell using non-aqueous 1M LiPF6 dissolved in EC-DEC. Charge discharge profiles are investigated as a function of the rate capability, the voltage window and the synthesis parameters of the cathode. A relation is found between the gravimetric capacity and the cation disorder of materials as indicated by magnetometry analysis.
Long-Term Stability of Primary Film Battery for Radio Frequency Identification(RFID) Tag and Ubiquitous Sensor Node
Authors: Lee Young-Gi , Yeo Junho , Pyo Cheol Sig , Kyhm Kwangseuk , Cho Kuk Young , Ryu Kwang Sun 
Published: April 2011

ABSTRACTWe have prepared a primary film battery which shows improved shelf life and long-term stabiltiy. We tried to optimize a multi-layered packaging film by considering gas permeability, chemical affinity, and film thickness. We also optimized conducting layer thickness, cathode/anode thickness and their compositions taking N/P rato into account. We introduced a variety of hydrogel polymers, newly developed electrolyte solutions, and novel separators to enhance the ionic conductivity value of gel-type polymer electrolyte/separator system for peak power and high power property.
Synthesis, Structure, and Electrochemical Properties of Li4Ti5O12
Authors: Ramana Chintalapalle V , Utsunomiya Satoshi , Ewing Rodney C , Becker Udo , Zaghib Karim , Julien Christian M 
Published: April 2011

ABSTRACTLithium titanium oxide (Li4Ti5O12) spinels are promising negative electrode materials for application in energy technology. In this work, we have synthesized Li4Ti5O12 and investigated its structure, electronic properties, and electrochemical features using several analytical spectroscopy and microscopy techniques. The equally spaced lattice fringes obtained using by the high-resolution transmission electron microscopy (HRTEM) along with electron diffraction reveal that the grown Li4Ti5O12 is well crystallized in the spinel structure without any indication of crystallographic defects such as dislocations or misfits. The electronic structure determination using high-resolution X-ray photoelectron spectroscopy (XPS) coupled with compositional studies using energy dispersive X-ray spectrometry (EDS) indicate excellent chemical quality of the Li4Ti5O12. Under the optimal synthetic condition, the sample delivers a discharge capacity of 161 mAh/g at C/12. The good cyclability of Li4Ti5O12 is attributed to the small expansion (δV≈1%) of the elementary unit-cell.
Improvement of Photovoltaic Response Using Triplet Excitons
Authors: Xu Zhihua , Hu Bin 
Published: April 2011

ABSTRACTWe report an enhancement of photovoltaic response by dispersing phosphorescent dye fac tris (2-phenylpyridine) iridium (Ir(ppy)3) in organic solar cells of poly[2-methoxy-5-(2¡¦-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) doped with surface-functionalized fullerene 1-(3-methyloxycarbonyl)propy(1-phenyl [6,6] C61 (PCBM). It is known that photoexcitation generates both singlet and triplet states through intersystem crossing caused by hyperfine or spin-orbital coupling. Due to long diffusion length the triplet excitons can migrate from their generation sites to the interfaces of donor-acceptor interaction and directly dissociate into charge carriers. We found, based on the studies of magnetic field-dependent photocurrent, that the dispersed Ir(ppy)3 molecules increase the spin-orbital coupling strength and triplet density in the MEH-PPV matrix due to the penetration of MEH-PPV π electrons into the large field of orbital dipoles of the Ir(ppy)3. Especially, the triplet excitons facilitate the direct dissociation into charge carriers at the donor-acceptor interacting interfaces in the composite of MEH-PPV and PCBM, and consequently improve the photovoltaic response in organic solar cells.
Novel Nanoscale Organic Materials for Optimal Photovoltaic Functions
Authors: Chen Lin X , Polshakov Dmitrii , Xiao Shengqiang , Liang Yongye , Yu Luping 
Published: April 2011

ABSTRACTCovalently linked electron donor (D) and electron acceptor (A) with conjugated organic building blocks are novel materials for potential solar cell applications, because these molecular p-n junctions can minimize the exciton diffusion and transform the charge separation from interdomain to intramolecular processes. Hence, the bottleneck of the exciton diffusion in many bulk heterojuction materials can be eliminated. Meanwhile, these planar conjugated assemblies, such as supermolecules, multiblock oligomers and polymers, have strong tendency to π-π stacking to form continuous channels for charge carriers to hop/diffuse to respective electrodes. A quartet D-A assembly has been synthesized with bis-oligothiophene (BOTH) and bis-perylenediimide (BPDI) derivatives attached to a benzo template. The electronic structures and dynamics of photoinduced charge separation and recombination of this quartet molecule and reference compounds in solutions and films were studied at isolated the molecular level in solutions as well as at the molecular assembly level in films with stacked structures. Two different dynamics of charge separation and recombination associated with two types of donor/acceptor pair conformations in solution were observed. This molecular system exhibits a more efficient charge separation than charge recombination processes in both polar and non-polar organic solvents, as well as films. More efficient charge separation and slower charge recombination due to the covalent linkage indicating that the material is a potential candidate for photovoltaic studies in solid-state.
High-Efficiency Dye-Sensitized Solar Cell Based on ZnO Nanorod Arrays Electrode
Authors: Charoensirithavorn Patcharee , Yoshikawa Susumu 
Published: April 2011

ABSTRACTWe have fabricated transparent ZnO nanorod arrays on the fluorine-doped SnO2 transparent conducting oxide (FTO) glass substrates and used them as the wide band gap semiconductor in dye-sensitized solar cells. Our objectives are to introduce and demonstrate new possibilities in designing the semiconductor morphology. The best performance with this cell structure produced an open circuit voltage (Voc) of 0.64 mV, a short circuit current density (Jsc) of 5.37 mA/cm2, a fill factor (FF) of 0.49, and a conversion efficiency (η) of 1.69 %, primarily limited by the surface area of the nanorod array.
Influence of Nitrogen Doping on Tungsten Oxide Thin Films for Photoelectrochemical Water Splitting
Authors: Cole Brian , Marsen Bjorn , Miller Eric 
Published: April 2011

ABSTRACTThin films of tungsten oxide were investigated for use as a top junction in a hybrid photoelectrode. To increase the solar to hydrogen efficiency, the tungsten oxide requires a bandgap reduction to the range of 2.2 to 2.4 eV. Nitrogen doping of WO3 films was employed to reduce the bandgap via valence band modification. For low levels of doping, the bandgap was observed to increase, an effect attributed to decreased size of the polycrystals in the film. The photoelectrochemical efficiency was found to decrease from 80% for pure WO3 to 56% for films deposited at a nitrogen partial pressure of 1.5 mTorr. For even higher doping levels (to 5 mTorr N2), the bandgap was shown to decrease to a value of ∼1.9 eV, but the structural data indicates that significant disorder had been introduced. This disorder is consistent with recurrent dislocations, an effect that is common for the tungsten oxide material.
High Deposition Rate of Microcrystalline Silicon for n-i-p Solar Cell by Using VHF PECVD Method
Authors: Liu Jun-Chin , Huang Chin-jeng , Wong Techi , Wu Jian-Shu , Luo Yih-Rong , Chen Chi-Lin 
Published: April 2011

ABSTRACTP doped, intrinsic, and n doped microcrystalline silicon (μc-Si) thin films were successfully synthesized on 10×10 cm2 transparent conductive oxide (TCO) /glass substrate by using a Very High Frequency Plasma Enhanced Chemical Vapor Deposition (VHF-PECVD, 80MHz) single chamber system. The crystal fraction of p and n type μc-Si:H with a thickness of 100nm was over 70% and 80%, respectively. Intrinsic μc-Si:H was deposited at a substrate temperature of 250°C with a high deposition rate over 1 nm/s. Photo-current/dark-current ratio of intrinsic μc-Si:H was higher than 102. The optimum cell initial efficiency of μc-Si:H single junction solar cell had been achieved 7.03 % so far.
Microstructure Evolution in Deformed Copper and Nickel
Authors: Landau Peri , Shneck Roni Z. , Makov Guy , Venkert Arie 
Published: April 2011

ABSTRACTThe combined effect of strain and temperature on the microstructure and detailed internal structure of dislocation boundaries was systematically studied in compressed pure polycrystalline copper and nickel and compared to the microstructure of compressed polycrystalline aluminum. Below 0.5Tm the microstructure of Cu and Ni consists of dislocation cells, however, only in Cu second generation microbands are formed. In Cu and Ni, the dislocations inside the boundaries rearrange themselves from tangles to ordered arrays of parallel dislocations following interplay between strain (requirement for cross slip) and temperature (dislocation mobility and ease of cross slip). The ordered detailed structure is similar to that observed in Al deformed at room temperature and lower strain levels. The amount of strain and temperature applied to Cu and Ni in order to achieve the same detailed structure formed in Al depends on the stacking fault energy (SFE) of the metal- higher strain and temperature as the SFE is lower.
High Quality a-Ge:H Films and Devices Through Enhanced Plasma Chemistry
Authors: Johnson Erik V. , Roca i Cabarrocas Pere 
Published: April 2011

AbstractWe present a material study on RF PECVD-grown a-Ge:H showing that thin films of such material can be produced without using the conventional techniques of high power density or powered-electrode substrate placement. We demonstrate the production of material with PDS signatures superior to material produced at ten times higher power density. This is achieved through the use of Ar and H2 dilution and by growing the films at high pressures under conditions where nanocrystals formed in the gas phase contribute significantly to the growth as confirmed by HRTEM. The conditions described result in material which demonstrates activated conduction down to room temperature. Additionally, the quality of the material has been demonstrated through its application in n-i-p diodes. A spectral response at 0.9um of 0.38 and an AM1.5 efficiency of 2.1% have been demonstrated utilizing an absorber layer thickness of only 60nm.
Low Temperature High Quality Growth of Silicon-Dioxide Using Oxygenation of Hydrogenation-Assisted Nano-Structured Silicon Thin Films
Authors: Rouhi Nima , Esfandyarpour Behzad , Mohajerzadeh Shams , Hashemi Pouya , Hekmat-Shoar Bahman , Robertson Michael D. 
Published: April 2011

AbstractWe report a low temperature high quality oxide growth of nano-structured silicon thin films on silicon substrates obtained through a hydrogenation-assisted PECVD technique followed by a plasma enhanced oxidation process. The deposited layers were investigated and compared with respect to their electrical, optical and stoichiometrical properties by means of Ellipsometry, Rutherford backscattering (RBS), Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and by current voltage and capacitance voltage measurements on metal-oxide-semiconductor (MOS) structures.
Channel Reliability in MOSFETs with Gate Oxide Grown using ECR Plasma of O2/He
Authors: Jaju Vishwas , Dalal Vikram 
Published: April 2011

AbstractIn this paper we present the channel degradation properties of MOSFET with gate oxide grown using electron cyclotron resonance (ECR) plasma. Si was oxidized using ECR plasma of 10% O2/He at 450°C for 60 min. MOS and MOSFETs devices were fabricated, using ECR grown oxide as a gate oxide, to evaluate the electrical properties. We found that the n-MOSFET with ECR as-grown oxide shows poorer channel degradation properties, by approximately two orders of magnitude, compared to channel with thermally grown (at 950°C) dry oxide. When as-grown oxide was annealed at much higher temperature (~800oC), channel resistance for the hot carriers improved and became comparable to that of the thermally grown oxide. We have shown that because of the lower processing temperatures used during oxidation strain is present in the bulk oxide and also at Si-SiO2 interface. Annealing at higher temperature can relieve strain and this assumption was found be self consistent with the infrared absorption study.
Effects of Power Density and Thickness On Aluminum-Induced Crystallization of PECVD Amorphous Silicon
Authors: Hsu Kendrick S , Ou-Yang Jeremy , Ren Li P. , Pan Grant Z. 
Published: April 2011

AbstractThe effect of power density and thickness on aluminum-induced crystallization (AIC) of amorphous silicon (a-Si) formed with plasma enhanced chemical vapor deposition (PECVD) was studied by using N2-protected conventional furnace reaction and optical microscopy. With the deposition power density ranging from 0.05 to 1.00 W/cm2 and the thickness from 500 to 5000Å, it was found that a low power density as well as a large a-Si thickness could result in a decrease of activation energy and therefore a significant reduction of the AIC reaction temperature. Scanning and transmission electron microscopy and X-ray diffraction were used to check the crystallinity and quality of the AIC thin films. High quality polysilicon thin films were achieved at an AIC reaction temperature as low as 120°C.
Performance of Thin Film Silicon MEMS on Flexible Plastic Substrates
Authors: Patil Samadhan , Chu Virginia , Conde Joao Pedro 
Published: April 2011

AbstractMicroresonators based on thin film hydrogenated amorphous silicon microbridges were fabricated by surface micromachining on flexible polyethylene terephthalate (PET) substrates with a maximum processing temperature of 110°C. An aluminum sacrificial layer is used which is patterned by either wet etching or lift-off. Resonance in the MHz range was observed using electrostatic actuation. Processing of the microbridges on PET with sacrificial layer patterned by lift-off has higher yield than by etching. Bending measurements show that the thin film silicon microbridges on PET can withstand a higher compressive strain (-2.5%) than tensile strain (1.25%).
Effect of a Channel Length and Drain Bias on the Threshold Voltage of Field Enhanced Solid Phase Crystallization Polycrystalline Thin Film Transistor on the Glass Substrate
Authors: Lee Won-Kyu , Han Sang-Myeon , Park Sang-Geun , Chang Young-Jin , Park Kee-Chan , Kim Chi-Woo , Han Min-Koo 
Published: April 2011

AbstractWe have fabricated a new magnetic field enhanced solid phase crystallization (FESPC) polycrystalline silicon (poly-Si) thin film transistors (TFTs), which shows the excellent electrical characteristics and superior stability compared with hydrogenated amorphous silicon (a-Si:H) TFTs. The mobility (μ) and threshold voltage (VTH) of p-type TFTs of which the channel width and length are 5 μm and 7 μm, respectively are 31.98 cm2/Vs and -6.14 V, at VDS=-0.1 V. In the FESPC TFTs, the characteristics caused by grain boundary are remarkable due to large number of grain boundaries in the channel compared with poly-Si TFTs. The VTH of the TFT which have 5 μm channel length is smaller than that of 18 μm channel length by 1.36 V, which is considerably large value. It is due to the large number of grain boundaries in the channel and the high lateral electric field. The grain boundary potential barrier height is decreased, when the large lateral electric field is applied (which is called DIGBL effect). As a result of increased mobility, the drain current is increased, and VTH can be decreased. The activation energy (Ea) is strongly depended on the drain bias and the number of grain boundaries. is decreased, caused by the large drain bias and/or smaller number of grain boundaries. This decreased Ea can be reduced VTH due to increased the drain current. VTH of p-type poly-Si TFT employing FESPC on the glass substrate is affected by channel length and VDS due to energy barrier lowering effect at the grain boundary by increased lateral electrical field.
Improved Efficiency of Single Junction Microcrystalline Silicon n-i-p Solar Cells with an i-Layer Made by Hot-Wire CVD
Authors: Li Hongbo , Franken Ronald H.J. , Stolk Robert L. , van der Werf C. H.M. , Schuttauf Jan-Willem A. , Rath Jatin K. , Schropp Ruud E.I. 
Published: April 2011

AbstractThe influence of the surface roughness of Ag/ZnO coated substrates on the AM1.5 J-V characteristics of microcrystalline silicon (μc-Si:H) solar cells with an i-layer made by the hot-wire chemical vapour deposition (HWCVD) technique is discussed. Cells deposited on substrates with an intermediate rms roughness show the highest efficiency. When using reverse hydrogen profiling during i-layer deposition, an efficiency of 8.5 % was reached for single junction μc-Si:H n-i-p cells, which is the highest for μc-Si:H n-i-p cells with a hot-wire i-layer.
Hydrogen Passivation of Thin-film Polysilicon Solar Cells
Authors: Carnel Lode , Gordon Ivan , Van Gestel Dries , Beaucarne Guy , Poortmans Jef 
Published: April 2011

AbstractThin-film polysilicon solar cells are a promising low-cost alternative for bulk silicon solar cells. Due to their reduced material thickness, these solar cells are less dependent on the silicon feedstock price. Until now these devices showed a worse performance compared to bulk Si solar cells due to the small grain size and the high recombination velocity at the grain boundaries. A better understanding of hydrogen passivation is therefore of crucial importance to improve the efficiency of polysilicon solar cells. In this work we characterized fine-grained polysilicon layers with a grain size of only 0.2 μm before and after passivation. Plasma hydrogenation led to a higher hydrogen concentration in the first micron of the layer than nitride passivation. The highest efficiency of 5.0 % was reached when nitride passivation was followed by plasma passivation.