bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electronic Detection and Quantification of ions in solution using an a-Si:H Field-effect Device
Authors: Costa João , Fernandes Miguel , Vieira Manuela , Lavareda G. , Carvalho C. N. , Karmali Amin 
Published: June 2009

AbstractProgress in microelectronics and semiconductor technology has enable new capabilities in the field of sensor construction, particularly of pH sensors based on field-effect transistors (FETs) as transducers of chemical signal. While crystalline devices present a higher sensitivity, their amorphous counterpart present a much lower fabrication cost, thus enabling the production of cheap disposable sensors for use in the food industry. Interest in biosensors consisting of a semiconductor transducer and a functionalized surface with biomolecule receptors (BioFET) continues to grow as they hold the promise for highly selective, label-free, real-time sensing as an alternative to conventional optical detection techniques.
We have been involved in the development of a biosensor where the enzymatic activity of recombinant amidase from Escherichia coli is coupled to a semiconductor transducer for the detection of toxic amides in food and industrial effluents. The devices were fabricated on glass substrates by the PECVD technique in the top gate configuration, where the metallic gate is replaced by an electrolytic solution with an immersed Ag/AgCl reference electrode. Silicon nitride is used as gate dielectric enhancing the sensitivity and passivation layer used to avoid leakage and electrochemical reactions. In this article we report on the semiconductor unit, showing that the sensor displays the desired current-voltage characteristics. In addition we present an electrical model of the device, in agreement with the experimental data, that is sensitive to the pH of the solution.
Effects of electro-mechanical stressing on the electrical characterization of on-plastic a-Si:H thin film transistors
Authors: Chen Jian Z. , Chih-Yong Yeh , Chiu I-Chung , Cheng I-Chun , Huang Jung-Jie , Chen Yung-Pei 
Published: June 2009

AbstractWe analyzed the effect of electromechanical stressing on the electrical characteristics of hydrogenated amorphous silicon thin-film transistors. It had been shown that the TFTs, fabricated at 150 °C, respond to tension/compression by a rise/fall in electron mobility. In TFTs fabricated using the same process, a slight shift of threshold voltage was observed under prolonged high compressive strain and the gate leakage current slightly increases after ˜2% compressive strain. In general, the change of TFT performance due to pure mechanical straining is small in comparison to electrical gate-bias stressing. From the comparison among Maxwell stress (induced by electrical gate-bias stressing), mechanical stress (applied by bending), and drifting electrical force for passivated hydrogen atom, the most significant cause for the change of electrical characterization of a-Si:H TFTs should be the trapping charges inside the dielectric, under combined electrical and mechanical stressing. The mechanical stress does not act on Si-H bonds to drift hydrogen atoms, while it is mainly balanced by the rigid Si-Si networks in a-Si:H or a-SiNx. Therefore, mechanical stress has very little effect on the instability of low temperature processed a-Si:H TFTs.
Thin Film Silicon Solar Cells on Transparent Plastic Substrates
Authors: Fathi Ehsanollah , Sazonov Andrei 
Published: June 2009

AbstractIn this work, we optimized different thin film silicon layers in a single junction p-i-n solar cell at deposition temperature of 150 °C. Using the optimized doped and undoped layers, 0.5 cm2 test cells fabricated both on glass and polyethylene naphthalate (PEN) substrates. The cells show identical open circuit voltages and fill factors, whereas the short circuit current and consequently the efficiency of the cell fabricated on glass is higher than the efficiency of 3.99% of the cell fabricated on PEN substrate.
Comparative Study of MVHF and RF Deposited Large Area Multi-junction Solar Cells Incorporating Hydrogenated Nano-Crystalline Silicon
Authors: Xu Xixiang , Li Yang , Ehlert Scott , Su Tining , Beglau Dave , Bobela David , Yue Guozhen , Yan Baojie , Zhang Jinyan , Banerjee Arindam , Yang Jeff , Guha Subhendu 
Published: June 2009

AbstractWe report our investigations of large area multi-junction solar cells based on hydrogenated nano-crystalline silicon (nc-Si:H). We compared results from cells deposited by RF (13.56 MHz) at lower deposition rate (˜3 Å/s) and by Modified Very High Frequency (MVHF) at higher rate (≥ 10 Å/s). With optimized process conditions and cell structures, we have obtained ˜12% initial small active-area (˜0.25 cm2) efficiency for both RF and MVHF cells and 10˜11% large aperture-area (˜400 cm2) encapsulated MVHF cell efficiency for both a-Si:H/nc-Si:H double-junction and a-Si:H/nc-Si:H/nc-Si:H triple-junction structures on Ag/ZnO coated stainless steel substrate.
Low Temperature Direct Cu-Cu Immersion Bonding for 3D Integration
Authors: Agarwal Rahul , Ruythooren Wouter 
Published: June 2009

AbstractHigh yielding and high strength Cu-Cu thermo-compression bonds have been obtained at temperatures as low as 175°C. Plated Cu bumps are used for bonding, without any surface planarization step or plasma treatment, and bonding is performed at atmospheric condition. In this work the 25μm diameter bumps are used at a bump pitch of 100μm and 40μm. Low temperature bonding is achieved by using immersion bonding in citric acid. Citric acid provides in-situ cleaning of the Cu surface during the bonding process. The daisy chain electrical bonding yield ranges from 84%-100% depending on the bonding temperature and pressure.
Development of X-ray, Gamma Ray Spectroscopic Detector Using Epitaxially Grown Single Crystal Thick CdTe Films
Authors: Niraula Madan 
Published: June 2009

AbstractIn this paper, we review our efforts in the spectroscopic detector development using epitaxially grown thick single crystal films of CdTe. The films were grown on GaAs and Si substrates using metalorganic vapor phase epitaxy growth technique. High crystalline quality thick single crystal CdTe films (>260 μm) were obtained where the growth rates could be varied from 10 to 70 μm/h by adjusting the precursor's flow rates, ratios and the substrate temperatures. Spectroscopic detectors were fabricated in a p-CdTe/n-CdTe/n+-GaAs or p-CdTe/n-CdTe/n+-Si heterojunction diode structure. Both types of detector were capable of detecting and resolving energy peaks from a gamma ray source. However, the spectroscopic performance of p-CdTe/n-CdTe/n+-Si detectors was better than that of the p-CdTe/n-CdTe/n+-GaAs detectors. Details on the growth characteristics, detector fabrication and the detector performance are reported. Furthermore, current challenges in this detector fabrication technique are discussed.
Modeling the Crystal Growth of Cadmium Zinc Telluride: Accomplishments and Future Challenges
Authors: Derby Jeffrey , Gasperino David , Zhang Nan , Yeckel Andrew 
Published: June 2009

AbstractThe availability of large, single crystals of cadmium zinc telluride (CZT) with uniform properties would lead to improved performance of gamma radiation detectors fabricated from them. However, even though CZT crystals are the central element of these systems, there remains relatively little fundamental understanding about how these crystals grow and, especially, how crystal growth conditions affect the properties of grown crystals. This paper discusses the many challenges of growing better CZT crystals and how modeling may favorably impact these challenges. Our thesis is that crystal growth modeling is a powerful tool to complement experiments and characterization. It provides an important approach to close the loop between materials discovery, device research, systems performance, and producibility. Specifically, we discuss our efforts to model gradient freeze furnaces used to grow large CZT crystals at Pacific Northwest National Laboratories and Washington State University. Model results are compared with experimental measurements, and the insight gained from modeling is discussed.
Characterizing the effects of silver alloying in chalcopyrite CIGS with junction capacitance methods
Authors: Erslev Peter , Hanket Gregory M. , Shafarman William N. , Cohen David J. 
Published: June 2009

AbstractA variety of junction capacitance-based characterization methods were used to investigate alloys of Ag into Cu(In1-xGax)Se2 photovoltaic solar cells over a broad range of compositions. Alloys show encouraging trends of increasing VOC with increasing Ag content, opening the possibility of wide-gap cells for use in tandem device applications. Drive level capacitance profiling (DLCP) has shown very low free carrier concentrations for all Ag-alloyed devices, in some cases less than 1014 cm−3, which is roughly an order of magnitude lower than that of CIGS devices. Transient photocapacitance spectroscopy has revealed very steep Urbach edges, with energies between 10 meV and 20 meV, in the Ag-alloyed samples. This is in general lower than the Urbach edges measured for standard CIGS samples and suggests a significantly lower degree of structural disorder.
Theory of Recombination in Non-Crystalline Junctions
Authors: Nardone Marco , Karpov Victor G. , Shvydka Diana 
Published: June 2009

AbstractA theory of non-crystalline recombination junctions is developed and compared to the experimental data. Junction transport is represented as hopping in both real and energy spaces, dominated by rare yet exponentially effective optimum channels having favorable configurations of localized states. Our work correlates the current-voltage characteristics of non-crystalline devices with material parameters and predicts large non-ideality factors increasing under light, and possible variations between nominally identical devices.
High Temperature Thermoelectric Properties of Nano-Bulk Silicon and Silicon Germanium
Authors: Bux Sabah , Fleurial Jean-Pierre , Blair Richard G. , Gogna Pawan K. , Caillat Thierry , Kaner Richard B 
Published: June 2009

AbstractPoint defect scattering via the formation of solid solutions to reduce the lattice thermal conductivity has been an effective method for increasing ZT in state-of-the-art thermoelectric materials such as Si-Ge, Bi2Te3-Sb2Te3 and PbTe-SnTe. However, increases in ZT are limited by a concurrent decrease in charge carrier mobility values. The search for effective methods for decoupling electronic and thermal transport led to the study of low dimensional thin film and wire structures, in particular because scattering rates for phonons and electrons can be better independently controlled. While promising results have been achieved on several material systems, integration of low dimensional structures into practical power generation devices that need to operate across large temperature differential is extremely challenging. We present achieving similar effects on the bulk scale via high pressure sintering of doped and undoped Si and Si-Ge nanoparticles. The nanoparticles are prepared via techniques that include high energy ball milling of the pure elements. The nanostructure of the materials is confirmed by powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and dynamic light scattering. Thermal conductivity measurements on the densified pellets show a drastic 90% reduction in the lattice contribution at room temperature when compared to doped single crystal Si. Additionally, Hall effect measurements show a much more limited degradation in the carrier mobility. The combination of low thermal conductivity and high power factor in heavily doped n-type nanostructured bulk Si leads to an unprecedented increase in ZT at 1275 K by a factor of 3.5 over that of single crystalline samples. Experimental results on both n-type and p-type Si are discussed in terms of the impact of the size distribution of the nanoparticles, doping impurities and nanoparticle synthesis processes.
Syntheses of Ni-doped and Fe-doped CoSb3 Thermoelectric Nanoparticles through Modified Polyol Process
Authors: Itoh Takashi , Isogai Keisuke 
Published: June 2009

AbstractSkutterudite CoSb3 compounds are of increasing interest as materials with good thermoelectric performance over the temperature range of 600 to 800 K, but the thermal conductivity of the materials is relatively high. Nanostructured materials have been shown to enhance phonon scattering and lower the thermal conductivity of the thermoelectric materials. Partial substitution of Ni or Fe on the Co site of CoSb3 is a hopeful route for improving thermoelectric performance of the CoSb3 compounds. In the present work, synthesis of Ni-doped and Fe-doped CoSb3 nanoparticles through the modified polyol process was attempted and the optimum synthesizing condition was investigated. Co(OOCH3)2·4H2O, Ni(OOCH3)2·4H2O, FeCl3·6H2O and SbCl3, were prepared as precursors. The precursors were reduced by NaBH4 in tetraethyleneglycol at 513 K in an argon atmosphere, for different reaction times (holding times). The reaction products were characterized by the X-ray diffraction, the energy dispersive X-ray spectroscopy, and transmission electron microscopy. The nanoparticles with about 20 to 30 nm in size mainly existed in the reaction products regardless of the chemical composition and the reaction time. The skutterudite phase was identified as a main phase in the sample synthesized for long reaction time, but the other phases of Sb and MSb2 (M=Co, Ni, Fe) were also detected. The lattice parameter of the synthesized skutterudite phase linearly increased with increasing the doping agent concentration, following Vegard’s law.
Output Power Characteristics of Mg2Si and the Fabrication of a Mg2Si TE Module with a Unileg Structure
Authors: Nemoto Takashi , Iida Tsutomu , Oguni Yohei , Sato Junichi , Matsumoto Atsunobu , Sakamoto Tatsuya , Miyata Takahiro , Nakajima Tadao , Taguchi Hirohisa , Nishio Keishi , Takanashi Yoshifumi 
Published: June 2009

AbstractIn order to restrain global warming and to realize a sustainable global energy system, further enhancements in energy efficiency are required. One reliable technology for reducing greenhouse gas emissions and the consumption of fossil fuel is thermoelectric technology, which can directly convert heat into electricity and consequently increases the energy conversion efficiency of power generation by combustion. Magnesium silicide (Mg2Si) is a promising candidate for a thermal-to-electric energy-conversion material at operating temperatures ranging from 500 to 800 K. Mg2Si exhibits many promising characteristics, such as the abundance of its constituent elements in the earth’s crust and the non-toxicity of its processing by-products, resulting in freedom from concerns regarding prospective extended restrictions on hazardous substances.
The efficiency of a thermoelectric device is characterized by the dimensionless figure of merit, ZT. It is well known that several kinds of dopants are effective in improving the thermoelectric performance of n-type Mg2Si. With Bi-doped n-type Mg2Si, we have achieved a maximum value of the dimensionless figure-of-merit ZT of ˜1.0 at ˜ 850 K. However, the correlation between the ZT values and the power generation characteristics, which is essential to understand in order to design a structure for a TE power generation module, has not been sufficiently investigated. In order to design a structure for a thermoelectric module using Mg2Si, we examined the correlation between the ZT values and the power-output of a single element using Mg2Si (ZT = 0.6) and Mg2Si doped with donor impurities such as Al and/or Bi (ZT = 0.65˜0.77). The measured single element was 2×2 mm2 in section and 10 mm long. Additionally, we developed and evaluated a new architecture based on a ‘unileg’ structure Mg2Si TE power generation module, which can improve the module lifetime and simplify its manufacture. As a starting material for the fabrication of the single element and the TE modules, pre-synthesized polycrystalline Mg2Si, fabricated by UNION MATERIAL was used. The material was sintered using a plasma-activated sintering (PAS) technique, and, at the same time, Ni electrodes were formed on the Mg2Si by employing of a monobloc PAS technique. The thermoelectric power-outputs were measured under a temperature difference, ΔT, ranging from 100-to-500 K by using UNION MATERIAL UMTE-1000M.
The observed power-output for single element of Mg2Si (ZT = 0.6), 2 at % Bi-doped Mg2Si (ZT = 0.65) and 1at % Bi + 1at % Al-doped Mg2Si (ZT = 0.77) were 23.2 mW, 13.6 mW and 19.4 mW respectively at ΔT = 500 K (between 873 K and 373 K). For the new architecture based on the unileg structure thermoelectric module, the observed value for power-output-per-unit-area was 12 mW/mm2 at ΔT = 500 K.
Enhanced thermoelectric properties in PbTe Nanocomposites
Authors: Kirby Hillary , Martin Joshua , Datta Anuja , Chen Lidong , Nolas George S. 
Published: June 2009

AbstractDimensional nanocomposites of PbTe with varying carrier concentrations were prepared from undoped and Ag doped PbTe nanocrystals synthesized utilizing an alkaline aqueous solution-phase reaction. The nanocrystals were densified by Spark Plasma Sintering (SPS) for room temperature resistivity, Hall, Seebeck coefficient, and temperature dependent thermal conductivity measurements. The nanocomposites show an enhancement in the thermoelectric properties compared to bulk PbTe with similar carrier concentrations, thus demonstrating a promising approach for enhanced thermoelectric performance.
Fabrication of Nano-Sized Tin Oxide Powder by Spray Pyrolysis Process
Authors: Yu Jaekeun , Kim Jwayeon , Han Jeoungsu 
Published: June 2009

AbstractBy using tin chloride solution as the raw material, a nano-sized tin oxide powder with average particle size below 50 nm is generated by spray pyrolysis reaction. This study also examines the influences of the reaction parameters such as reaction temperature and the concentration of raw material solution on the powder properties. As the reaction temperature increases from 800 to 850 ℃, the average particle size of the generated powder increases from 20 nm to 30 nm. As the reaction temperature reaches 900 ℃, the droplets are composed of nano-particles with average size of 30 nm, while the average size of individual particles increases remarkably up to 80˜100 nm. When the tin concentration reaches 75 g/L, the average particle size of the powder is below 20 nm. When the tin concentration reaches 150 g/L, the droplets are composed of nano particles with average size around 30 nm, whereas the average size of independent particles increases up to 80˜100 nm. When the concentration reaches 400 g/L, the droplets are composed of nano-particles with average size of 30 nm.
Ferromagnetism and Near-infrared Luminescence in Neodymium and Erbium Doped Gallium Nitride via Diffusion
Authors: Luen Melvyn Oliver , Nepal Neeraj , Frajtag Pavel , Zavada John , Brown Ei , Hommerich Uwe , Bedair Salah M. , El-Masry Nadia 
Published: June 2009

AbstractIn this study, we report on the diffusion of neodymium (Nd) and erbium (Er) into n-type and undoped GaN and subsequent measurements of the room-temperature (RT) magnetic and optical properties. The diffusion profile has been measured via secondary ion mass spectroscopy (SIMS) with rare-earth (RE) concentration yields of up to 1×1018/cm3. The ferromagnetic properties were measured using an alternating gradient magnetometer (AGM) giving a saturation magnetization (Ms) of up to 3.17emu/cm3 for the RE-diffused layer. The photoluminescence (PL) emission of the Nd-diffused and Er-diffused GaN is observable in the near-infrared (NIR) and infrared (IR) regions of the spectrum, respectively. The Nd-diffused GaN samples show NIR emission at 1064nm and 1350nm, while Er-diffused GaN samples have IR emission at 1546nm. This appears to be the first successful result of Nd diffusion doping into GaN crystals, and the first demonstration of above RT ferromagnetism involving GaN diffused with Nd. Details of our ferromagnetic and optical emission studies, related to the RE diffusion into GaN, are presented.
Temperature-Dependent Structural Disintegration of Delafossite CuFeO2
Authors: Pavunny Shojan P , Kumar Ashok , Thomas Reji , Murari Nishit M , Katiyar Ram S 
Published: June 2009

AbstractSingle phase delafossite p-type CuFeO2 (CFO) semiconductor was synthesized in bulk by modified solid state reaction technique. X-ray diffraction (XRD) and X-ray photo spectroscopy (XPS) studies suggest single phase CFO at room temperature. The energy dispersive X-ray spectroscopy (EDX) revealed that the atomic ratio of Cu and Fe is 1:1. The XPS spectra showed two intense Cu 2p3/2 and 2p1/2 peaks at 932.5 eV and 952 eV suggesting Cu is in +1 state. The temperature dependent Raman spectra of CFO displayed two intense modes at 349 cm-1 and 690 cm-1 at room temperature that matched with other delaffosite structures. The temperature dependent Raman spectra showed significant shift in both Raman active modes to lower frequency side. We observed the disappearance of pure CFO Raman active modes above 750 K and the appearance of new peaks related to CuO compounds, indicating disintegration of CFO starting above 750 K which almost completed above 1100 K. The temperature dependent thermo-gravimetric analysis indicates change in CFO mass above 750 K with wide range of differential thermo-gravimetric slope suggests disintegration started above 750 K and completed at 1100 K. Raman spectra, XPS, and XRD of disintegrated CFO matched well with the Raman spectra, XPS and XRD of CuO and CuFe2O4 confirmed its disintegration above 750 K in air.
Image Deconvolution - An Effective Tool of Crystal Structure and Defect Determination in High-Resolution Electron Microscopy
Authors: Li Fanghua , Tang Chunyan 
Published: June 2009

AbstractImage deconvolution is introduced as an effective tool to enhance the determination of crystal structures and defects in high-resolution electron microscopy. The essence is to transform a single image that does not intuitively represent the examined crystal structure into the structure image. The principle and method of image deconvolution together with the related image contrast theory, the pseudo weak phase object approximation (pseudo WPOA), are briefly described. The method has been applied to different types of dislocations, twin boundaries, stacking faults, and one-dimensional incommensurate modulated structures. Results on the semiconducting epilayers Si0.76Ge0.24/Si and 3C-SiC/Si are given in some detail. The results on other compounds including AlSb/GaAs, GaN, Y0.6Na0.4Ba2Cu2.7Zn0.3O7-δ, Ca0.28Ba0.72Nb2O6and Bi2.31Sr1.69CuO6+δare briefly summarized. It is also shown how to recognize atoms of Si from C based on the pseudo WPOA, when the defect structures in SiC was determined at the atomic level with a 200 kV LaB6microscope.
Advanced TEM Characterization for Catalyst Nanoparticles Using Local Adaptive Threshold (LAT) Image Processing
Authors: Bele Petra , Stimming Ulrich 
Published: June 2009

AbstractMetallic and non-metallic nanoparticles, usually supported on non-metallic substrates have attracted much interest concerning their application in the field of electrocatalysis. To characterize catalysts with respect to size, morphology, structure and composition (alloys or core-shell) of nanoparticles and their associated electrocatalytic activity, transmission electron microscopy (TEM) is the state of the art method. This investigation shows the advantages of advanced image processing using the local adaptive threshold (LAT) routine.