bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Examination of the Deformation Process in Equal-Channel Angular Pressing
Authors: Berbon Patrick B. , Furukawa Minoru , Horita Zenji , Nemoto Minoru , Langdon Terence G. 
Published: April 2011

AbstractIn the past decade, there has been an important emphasis in materials science on the production and use of ultrafine-grained materials. These materials offer wide-ranging advantages such as an improvement in strength at low temperatures and enhanced superplastic behavior at high temperatures. New techniques to process these materials have been developed. Good properties have been achieved by powder metallurgy and by techniques of bulk processing. Equal-channel angular (ECA) pressing is a bulkprocessing technique which has led to some remarkable achievements in the production of sub-microcrystalline materials with excellent superplastic properties at low temperatures and high strain rates. When considering the currently available physical and mechanical properties of these materials, it appears that some aspects cannot be explained solely by the very small grain size. In fact, the specific mode of deformation occurring in ECA pressing appears to have an influence on the final properties. This paper reviews the details of this metal working technique and then provides an explanation for the observed microstructures, their thermal stability and their remarkable superplastic properties.
Superplastic Properties of an Aluminum-Based Alloy After Equal-Channel Angular Pressing
Authors: Wang Jingtao , Berbon Patrick B. , Xu Yuzhong , Wang Lizhong , Langdon Terence G. 
Published: April 2011

AbstractIt is now recognized that superplasticity requires a very small grain size, typically > 10 μm. A further reduction in grain size, to the submicrometer or nanometer level, offers the potential for attaining superplasticity at both faster strain rates and lower temperatures. This paper reports an investigation of the microstructure and tensile behavior of an Al-3% Mg-0.5% Zr alloy after processing by equal-channel angular pressing to an equivalent true strain of ∼8.
Comparative Study of Structural and Néel Transition Temperatures in FE-MN-SI Shape-Memory Alloys
Authors: da Silva M.I.N. , de Arruda G.J. , Côrtes P.E.F. , Andrade M.S. , Paniago R. , Speziali N.L. 
Published: April 2011

AbstractFe-Mn-Si based alloys exhibit the shape memory effect depending on their composition. Upon cooling, these alloys undergo a martensitic transformation γ (fcc) → ε (hcp), and a magnetic transition, at the Néel temperature, from paramagnetic to antiferromagnetic ordering in the γ-phase. In this work, the structural and magnetic phase transition temperatures were determined in an Fe-27Mn-2.5Si (in weight %) shape-memory alloy, using differential scanning calorimetry, dilatometry, electrical resistivity, Mossbauer spectroscopy, and X-ray diffraction. The transition temperatures measured by the different techniques were almost the same. It was observed, by calorimetry and electrical resistivity measurements, that the magnetic transition temperature upon cooling was very close and slightly higher than that of the start of the martensitic transformation, thus promoting the stabilization of the γ-phase. Consequently, the amount of thermally induced ε-martensite was very small. Mössbauer spectroscopy and X-ray diffraction measurements showed that only 10% of ε-martensite was formed upon cooling to quite low temperatures.
Molecular Recognition of Organic Compounds by Imprinted Silica
Authors: Gong Xiaoyi , Liu Jun , Samuels William D. 
Published: April 2011

AbstractSpecific interactions between silica and organic molecules play an important role in molecular imprinting, molecular recognition, and enzyme activity. To understand the specific interactions, six pairs of organic compounds were chosen and investigated for their molecular imprinting capabilities on silica. Silica adsorbents imprinted by methyl red or ρ-methyl red, methyl orange or ethyl orange, and histidine-alanine or histidine-leucine can recognize their imprinting molecules. Silica samples “imprinted” with methyl red or ethyl red, 4,9-diaminoflourenone or 3,3'-diaminodiphenylmethane, and l-histidine or d,l-histidine do not recognize their “imprinting” molecules. The molecular recognition is related to the structure of the imprinting molecules. The following lessons were learnt: 1) Three or more strong interaction sites on the imprinting molecules are necessary to endow silica with recognition capability; 2) Position of functional groups is more important than their size to achieve the molecular recognition; 3) Chiral recognition needs stronger interaction and/or more interaction sites
Control of Residual Stresses in As-Grown Polysilicon by Multi-Layer Deposition: The “Multipoly” Process
Authors: Yang Hie , Kahn H. , He A.Q. , Phillips S.M. , Heuer A.H. 
Published: April 2011

AbstractLPCVD polysilicon thin films deposited between ∼550 and ∼600 °C have an equiaxed microstructure (resulting from crystallization of an initially amorphous deposit) and contain ∼200 MPa residual tensile stresses after deposition, whereas polysilicon films deposited above ∼600 °C have a columnar microstructure and contain ∼300 MPa residual compressive stresses after deposition. Both types of films also contain stress gradients.We have grown films containing multiple layers of polysilicon ("MultiPoly") by cycling the growth temperature between 570 and 615 °C. The multilayer films thus formed are comprised of alternating tensile and compressive layers, and by control of the thickness of the individual layers, the overall stress of the polysilicon can display any value between that of the tensile layer and that of the compressive layer. We have focussed on producing films with zero overall residual stress, as measured by wafer curvature, and have characterized the microstructures by transmission electron microscopy (TEM) and X-ray diffraction (XRD).Because of the stress gradients present in both layers, devices made from films with zero overall residual stress may show distortions after release. We have measured the stress gradients in each type of layer and can design films with zero overall stress and zero overall stress gradients. It is also possible to design films with any level of overall (tensile or compressive) stress but with controlled displacements upon release.
High-Resolution Measurement of Crack Growth in Micro-Machined Crystal Silicon
Authors: Fitzgerald A.M. , Dauskardt R.H. , Kenny T.W. 
Published: April 2011

AbstractTime dependent sub-critical cracking associated with environmental species such as moisture may have significant implications for the reliability of MEMS devices made of silicon. However, the existence of such stress corrosion phenomena in silicon remains controversial. Sub-critical crack-growth behavior in brittle materials is commonly characterized using crack velocity versus applied stress intensity curves (v-K curves). Crack velocity is inferred by curve-fitting crack length versus time data taken at low sample rates (<100 Hz) under the assumption that crack growth is a continuous process. However, we have observed discrete crack growth behavior in a micro-machined compression-loaded double cantilever beam. The samples are fabricated from (100) single crystal silicon wafers. A thin film resistor sputtered onto the sample surface using a lithographic technique is used to directly measure crack extension. The crack growth in all samples is characterized by periods of rapid crack growth interspersed with long periods of arrest in which no evidence of sub-critical cracking was observed. High speed data acquisition (up to 100 MHz) was performed and crack velocities as high as 1.7 km/s were accurately measured during these rapid growth periods.
Group III Metal Sulfide Thin Films From Single-Source Precursors by Chemical Vapor Deposition (CVD) Techniques
Authors: Lazell Mike R. , O'brien Paul , Otway David J. , Park Jin-Ho 
Published: April 2011

AbstractSeveral single-source precursors including In(SOCNiBu2)3, In(S2CNMeHex)3 and Ga(S2CNMeR)3, (R = Et, Bu, Hex) have been prepared and used for the deposition of Group 13 metal sulfide thin films. The α and β-In2S3thin films on borosilicate glass and oc-Ga 2S3thin films on GaAs(111) single crystal substrates were prepared from the precursors by various chemical vapour deposition (CVD) techniques. These semicondcuting materials have been characterized by XRD, SEM, XPS and EDAX.
Direct Fabrication of LiCoO2 Film Electrodes Using Soft Solution-Processing in LiOH Solution at 20 - 200°C
Authors: Song S.W. , Han K.S. , Yoshimura M. , Sato Y. , Tatsuhiro A. 
Published: April 2011

AbstractApplication of Soft Solution-Processing, which is defined by environmentally friendly processing using (aqueous) solution, to the field of rechargeable lithium microbattery has been demonstrated by fabricating LiCoO2 film on the cobalt metal substrate in LiOH solution under hydrothermal condition. The film formation mecahnism could be interpreted in terms of chemical dissolution of cobalt metal plate in LiOH solution at fixed temperature of 20 - 200°C, resulting in the formation of H1−nCoO2 where n value increases with fabrication temperature and precipitation as LiCoO2 by heterogeneous nucleation on the substrate followed by crystal growth. The crystal structure and film properties have been characterized by X-ray diffraction, X-ray photoelectron, micro-Raman spectroscopic and scanning electron microscopic analyses. The films exhibited a good crystallinity despite the low reaction temperature without any postsynthesis annealing. The films prepared under different conditions showed different phase selection such as spinel (Fd3m) or hexagonal (R3-m), surface morphology and film thickness. An electrochemical activity of the LiCoO2 films was evidenced by cyclic voltammogram revealing a good reversibility on Li-intercalation and -deintercalation.
Growth and Studies of Li (Mn, Co) Oxides for Battery Electrodes
Authors: Nieto-Ramos S. , Tomar M.S. , Katiyar R.S. 
Published: April 2011

AbstractThere is interest in lithium intercalation oxide materials for cathodes in rechargeable batteries. We have synthesized LiMOx, (where M = Mn, Co) by a less expensive solution route. Reagent grade acetates or hydroxides as precursors for lithium, manganese, and cobalt, respectively, with methoxy ethenol and acetic acid as solvents were used. Powders with different compositions were achieved at annealing temperature below 700 °C. Thin films were deposited by spin coating. X-ray diffraction, Raman spectroscopy, and impedance spectroscopic results are presented. These studies indicate that this synthetic route is suitable to produce good quality lithium-based oxides useful for cathode in lithium-ion rechargeable battery.
Crystallographic Orientation in Bulk Polycrystalline Silicon Carbide Produced by a Chemical Vapor Deposition (CVD) Process
Authors: Marzik James V. , Croft William J. 
Published: April 2011

AbstractPolycrystalline, theoretically dense silicon carbide was deposited onto graphite substrates via the reductive pyrolysis of methyltrichlorosilane in a hot-walled chemical vapor deposition (CVD) chamber. The resulting product can be considered a bulk material with deposit thicknesses in the range of 4 to 8 millimeters. The material was characterized using powder x-ray diffraction and Laue back-reflection techniques. Under the deposition conditions investigated in this study, the crystallographic orientation varied as a function of distance from the substrate. The material exhibited a high degree of randomness in proximity to the substrate, and progressively showed a higher degree of preferred crystallographic orientation as the deposit progressed. This phenomenon is correlated with the microstructure of the material as well as such mechanical properties as hardness and fracture toughness.
The Control of Zn for ZST Microwave Ceramics With Low Sintering Temperature
Authors: Park Yong H. , Shin Moo Y. , Ryu Ji M. , Ko Kyung H. 
Published: April 2011

AbstractZnO addition for low-T sintering of ZST has serious side effects such as decrease of Q × f value. In this work, the curing of these side effects without any further chemical additivesand causing degradation of other dielectric properties have been presented. After sintered at 1350°C for 2h. samples were annealed in oxygen at 900 ∼ 1100°C for 5hr. It was observed that Q × f value of post-annealed sample at 900°C could recovered up to 46000 from the as-sintered value of 40000. Because there were no formations of second phases or significant changes inlattice constants, which could affect microwave properties of ZST. However, it was found that only for the specimens annealed at 900°C, Zn was almost depleted from grin inside and diffused toward grain boundary. So, it is suggested that the out-diffusion of Zn is responsible for the recovery of Q × f value. Moreover, when the amount of Zn incorporation increased via successive calcination and sintering of pre-mixed powder of ZST and ZnO, Q × f value of 33000 also could enhanced up to 39000 due to the redistribution of Zn near grain boundary by out-diffusion.
Application of Pulsed Injection MOCVD to the Deposition of Dielectric and Ferroelectric Oxide Layers and Superlattices
Authors: Senateur Jean-Pierre , Lindner Johannes , Weiss François , Dubourdieu Catherine , Jimenez Carmen , Abrutis Adolfas 
Published: April 2011

AbstractThe technique used for the control of the injection of fuel in thermal motors has been applied to the generation of active gases for MOCVD layers deposition. A wide variety of compounds and multilayers have already been grown using this new CVD source (from simple cxides, nitrides or metals to complex ternary oxides). Using two injection sources working sequentially, stackings like YBa2Cu307/CeO2 or SrTiO3/YBa2Cu3O7 double layers, Ta2O5/SiO2 amorphous or crystallized multilayers and SrTiO3/BaTiO3 or YBa2Cu3O7/PrBa2Cu3O7 epitaxial superlattices have been synthesized. The injection MOCVD seems to be a very promising technique for the stacking of multicomponents oxides having different electronic properties. This opens the way for the synthesis of a wide set of artificial materials, exhibiting completely new properties that cover a very large range of potential applications. After a description of the technique, we will demonstrate its performances on some results obtained on the synthesis of dielectric and ferroelectric layers and multilayers.
The Longest Wavelength OPO Pumped by a 1µm Laser
Authors: Vodopyanov K.L. , Maffetone J. , Zwieback I. , Ruderman W. 
Published: April 2011

AbstractSingly resonant type-il AgGaS2OPO yielded continuously tunable 3.9–11.3 µm idler output with slope quantum efficiency up to 41 % (absolute photon efficiency 22%). The OPO has sub-100 µJ threshold pump energies for nanosecond 1.06µm Nd:YAG laser pulses.
Performance and Spectral Response of Far-Infrared Pb1−xSnxTe(In) Photodetectors
Authors: Ivanchik I. , Khokilov D. , Pipher J. , Raines N. , Watson D. 
Published: April 2011

AbstractDirect comparison of performance has been done for a Pb1−xSnxTe(In) photodetector, a Si(Sb) BIB structure and a state of the art Ge(Ga) photoconductor in the integration cavity. The PblSnTe(In) photodetector shows several orders of magnitude higher responsivity S, then the Si(Sb) BIB at the wavelength λ ∼ 14 µm. Persistent photoresponse with SI ∼ 103 A/W at 40 mV bias and 1 s integration time at the wavelengths of, λ = 90 and 116 µm has been observed for the first time for the Pb1−xSnxTe(In) photodetector. This value is by a factor of ∼ 100 higher than the respective parameters of the Ge(Ga) photoconductor in the same conditions.
Mechanisms of Intersubband Transition in n-Type III-V Quantum Well Superlattice and Improvement on Absorption for TE Polarized Field
Authors: Cheah C. W. , Karunasiri G. , Tan L. S. 
Published: April 2011

AbstractIn this paper, the theoretical study of intersubband transitions in quantum well infrared photodetectors (QWIPs) applying the eight bands k.p model incorporated with envelope function approximation is described. The focus of the work is on the intersubband transition in n-type IIIV QWIP based on AIGaAs/GaAs and AlGaAs/InGaAs material system, with particular emphasis placed on the physics of TE excited transition and the improvement of resulted absorption. Various theoretical absorption spectra of the two material systems are compared, the distinct mechanisms of the intersubband transition for the two material systems are proposed. Possible ways of improving on the absorption for such excitation are also investigated and discussed.
High-Resolution X-ray Diffraction Analysis of p-Type Strained InGaAs/AlGaAs Multiple Quantum Well Structures
Authors: Shi W. , Zhang D. H. , Osotchan T. , Zhang P.H. , Yoon S. F. , Swaminathan S. 
Published: April 2011

AbstractBe-doped InGaAs/AIGaAs multiple quantum well (MQW) structures, grown by solid-source molecular beam epitaxy with different doping concentration in the wells, were investigated by xray diffraction and transmission electron microscopy (TEM). Some features have been observed. (1) The MQW mean mismatch increases from 1.176 × 10−3 to 1.195 × 10−3 and 1.29 × 10−3 for the structures with doping concentration of 1 × 1017 cm−3, 1 × 1018cm−3and 2 × 1019 cm−3 in the wells, respectively. (2) The period of the MQW also increases with doping density. (3) The intensity of the first order satellite in the rocking curves decreases as the Be concentration is increased, indicating that indium diffusion in the heavily doped wells is likely more significant than that in the lightly doped ones. (4) The full width at half maximum of the zero-order satellite peak becomes widened as doping concentration increases, indicating that high Be-doping in the well likely deteriorates the interfaces of the multiple quantum well stacks. In addition, TEM measurement is conducted and clear pictures on well and barrier layers of the structures are observed. The information obtained is of great value for the design of p-doped quantum well infrared photodetectors.
The Development of Infrared Photosensitive Material Based on Polycrystalline PbS Films
Authors: Abarbanel C. , Shneck R. , Dashevsky Z. , Rotman S. 
Published: April 2011

AbstractPolycrystalline thin films of lead sulphide were deposited on glass substrates by the hot wall technique. The grain size varied from 100 to 500 A by varying the growth rate and the substrate temperature. The grain boundaries are assumed to influence the optoelectronic properties of polycrystalline films by generating potential energy relieves, estimated to reach 0.1 eV. We investigated the influence of the barrier height by introducing impurity atmospheres into the grain boundaries. Oxygen and indium were introduced into the films by diffusion from a gas phase. Conductivity was measured in the 80-300 K range. It rises with increasing temperature in oxygen doped films, indicating that conductivity is a thermal activation process. In the same time the conductivity of In doped PbS films decreases with temperature like in PbS single crystals. Photoconductivity was observed in films annealed in oxygen, which was significant up to room temperature. Carrier lifetime was found to decrease with rising temperature and be larger in films annealed in oxygen.A model is proposed to explain the optoelectronic behavior of the polycrystalline films. It is proposed that charge accumulation near grain boundaries set up potential barriers for free carriers. The barriers increase by oxygen and decreases by indium doping. The charge carriers generated by an illumination become spatially separated at grain boundaries. This separation retards their recombination and increases their lifetime, giving rise to persistent photoconductivity and potential high photosensitivity.
Evidence of High Electron Mobility in CdGeAs2 Single Crystals
Authors: Rud' V.Yu. , Rud' Yu.V. , Pandey R. , Ohmer M. C. 
Published: April 2011

AbstractCdGeAs2 single crystals were prepared by low temperature crystallization from a nonstoichiometric melt. The results of the first study of the temperature dependencies of the electrical conductivity and the Hall coefficient of n-type CdGeAs2 single crystals prepared by this new technique are reported. All the as-grown crystals show n-type conductivity. These single crystals had free electron concentrations of (1 - 2) 1018 cm−3 and Hall mobilities of more than 10000 cm2/(Vs) at T=300 K. These room temperature electron mobility values are four times larger than previously reported. In the high temperature region (T> 150K), the temperature dependence of the Hall mobility exhibited a behavior characteristic of phonon scattering. Below 150 K, a deviation from this behavior indicated an increasing contribution of static lattice defects to scattering. The Hall mobility in these crystals was found to reach ∼ 36000 cm2/( V· s ) at 77 K. The first photosensitive n-type CdGeAs2/n-type InSe heterostructures were constructed by contact methods. Photosensitivities of 70-100 V/were observed. This is substantially better than for previous structures using conventionally grown CdGeAs2 and indicates the high quality of the crystals. It is concluded that the low temperature growth technique is promising for the preparation of more perfect CdGeAs2crystals.
Modeling of the Properties of Dopants in the NLO Semiconductor CdGeAs2
Authors: Pandey Ravindra , Ohmer Melvin C. , Costales A. , Recio J. M. 
Published: April 2011

AbstractThe results of a shell-model study on CdGeAs2 doped with Cu, Ag, B, Al, Ga, and In are presented here. The pairwise interatomic potential terms representing the interaction of dopants with the host lattice ions are derived using first principle methods while empirical fitting methods are used for the host-lattice potentials. Defect calculations based on Mott-Littleton methodology predict small binding energies for Cu and Ag substituting Cd in the lattice which are in agreement with the available experimental data. The group III dopants (i.e. B, Al, Ga and In) at the Ge site are predicted to have large binding energies for a hole placing acceptor levels in the middle of the band gap.
ITO/a-SiNx:H/a-Si:H Photodiode with Enhanced Photosensitivity and Reduced Leakage Current Using Polycrystalline ITO Deposited at Room Temperature
Authors: Tao S. , Ma Q. , Striakhilev D. , Nathan A. 
Published: April 2011

ABSTRACTWe report an ITO/a-SiNx:H/a-Si:H MIS photodiode structure based on room temperature deposition of optically transparent polycrystalline ITO for applications in large area optical and x-ray imaging. The photodiode structure exhibits device characteristics with reduced leakage current and enhanced photosensitivity giving rise to a hundred-fold improvement in dynamic range. This notable improvement in performance is believed to be due to the reduced diffusion of oxygen from the ITO to the a-Si:H layer, and thus reducing the density of defect states inside the a-Si:H layer. The behavior of photo and dark current is consistent with an elaborate transport model for the Schottky barrier. The model agrees reasonably well with measurement data for the dark current and provides a consistent picture in terms of the photo current behavior in the MIS structure, where the insulating layer serves to reduce the oxygen diffusion.
Low gap Amorphous (Si,Ge) Solar Cells
Authors: Dalal Vikram L. , Zhou Zhiyang 
Published: April 2011

ABSTRACTWe report on the growth and fabrication of low-gap a-(Si,Ge) solar cells, including cells made from a-Ge:H. The cells were deposited from silane and germane, or germane alone, using a high dilution of hydrogen in a remote ECR plasma reactor. We have been able to achieve a Tauc gap of as low as 1.15 eV with good device properties. The fill factors were in the 50%-60% range, and the Urbach energies measured in devices were in the range of 45 meV. The devices were of the p/i/n type with light entering the p layer. The devices were fabricated on stainless steel substrates. We also report on experiments to improve graded gap solar cells in a- (Si,Ge) using a novel combination of ppm-boron dopant and bandgap grading. It is shown that this grading significantly improves the device performance, both voltage and fill factor.