bluuebunny/crossref_metadata_2025_split huggingface dataset:
Change of Ms Temperatures and its Correlation to Atomic Configurations of Offstoichiometric NiTi-Cr and NiTi-Co Alloys
Authors: Hosoda Hideki , Fukul Toshihiko , Inoue Kanryu , Mishima Yoshlnao , Suzuki Tomoo 
Published: April 2011

ABSTRACTEffects of compositional deviation from the stoichiometry and Cr and Co additions on martensitic-transformation-slart and auslenite-start temperatures (Ms and As) of offstoichiometric NiTi alloys are investigated. Ms and As are determined using conventional differential thermal analysis (DTA), where the temperature range investigated is between 77K and 423K. Alloys are widely chosen with both Ni- and Ti-rich compositions, to which ternary elements, Cr and Co, are added. It is clearly shown that Ms and As in single phase regions are reduced with increasing amount of constituent element, Ni, and ternary elements, Cr and Co. On the other hand, Ms and As do not depend on Ti concentration when Ti concentration is more than 52mol.%. NiTi alloys are in two phase region in the case. Ms changes by Co at offstoichiometry are evaluated to be -15K / mol.% in Ni poor side and -30K / mol.% in Ni rich side. These values correspond to -22K / mol.% for the stoichiometric NiTi alloys. Also, effects of Cr on Ms are evaluated to be -65K / mol.% in Ni poor side and -45K / mol.% in Ni rich side. The former is similar to the Ms change in stoichiometric alloys, and the latter is close to our prediction of -30K / mol.% in comparison with the reported value of -120K / mol.% for stoichiometric alloys. It is concluded for offstoichiometric NiTi alloys that effects of ternary additions on Ms can be explained using electronic structures of ternary elements by taking atomic configurations into account, as well as the stoichiometric NiTi alloys. Effect of degree of order is also discussed.
Pseudoelasticity in High Strengthening Fcc Single Crystals
Authors: Chumlyakov Yu.I. , Kireeva I. V. , Kapasova G. S. , Litvinova E. I. 
Published: April 2011

ABSTRACTIt was experimentally shown that the achievement of a high deforming stress level due to dispersion hardening and solid solution strengthening of FCC single crystals with a low stacking-fault energy leads to the deformation mechanism changing from slip to twinning, the dependence of mechanical properties on a crystal orientation and a sign of applied stresses. During deformation by twinning at T<150–300K effects of pseudoelasticity associated with elastic twinning is observed.
Dynamic Aspects of Formation of Synthetic Membranes
Authors: Thies M. , Paradies H. H. , Clancy S. F. 
Published: April 2011

ABSTRACTA detailed physical analysis of data obtained from static light and dynamic light scattering experiments with polymer-like distearyldimethylammonium OH (DSDMA X) micelles has been undertaken at dilute and semidilute concentrations, and compared with those in the presence of racemic and enantiomeric anions, e.g. S-(+)-lactate or the R-(-)-enantiomer.
DNA Sequence Alignment and Critical Phenomena
Authors: Drasdo Dirk , Hwa Terence , Lässig Michael 
Published: April 2011

AbstractAlignment algorithms are commonly used to detect and quantify similarities between DNA sequences. We study these algorithms in the framework of a recent theory viewing similarity detection as a geometrical critical phenomenon of directed random walks. We show that the roughness of these random walks governs the fidelity of an alignment, i.e., its ability to capture the correlations between the sequences compared. Criteria for the optimization of alignment algorithms emerge from this theory.
The Structural Changes Induced by Anchored Polymers on Droplet and Bicontinuous Microemulsion
Authors: Lal Jyotsana , Auvray Loic 
Published: April 2011

ABSTRACTMacroscopically, phase changes (induced due to change of curvature) were observed on the introduction of PEG (polyethyleneglycol) grafted on lipids (anchored polymers) in the Winsor phases of microemulsion. Replacing some of the surfactant in the monolayers of the micro-emulsion with polymer grafted lipids changes the interaction between droplets of micro- emulsion and a greater increase in the percentage of anchored polymer in the monolayer might even bring about structural changes. The results on winsor phases, droplet microemulsions and bicontinous phases with anchored polymers as studied by Small Angle Neutron Scattering (SANS) are reported below, together with the contrast variation techniques used to characterize average curvature in the system.
Interfacially Confined Polymeric Systems Studied by Atomic Force Microscopy
Authors: Overney René M. , Guo Lantao , Totsuka Hirono , Rafailovich Miriam , Sokolov Jonathan , Schwarz Steven A. 
Published: April 2011

ABSTRACTWithin the last few years, a surface science technique, the atomic force microscopy (AFM), has evolved to be capable of simultaneously measuring tribological (friction, wear, adhesion) and rheological (elastic moduli, viscosity, hardness) properties and topography on the nanometer scale. Particularly for thin polymeric films, the AFM can be efficiently used for studying surface mechanical properties which are of fundamental importance to help predict stress and frictional behavior of interfacially confined ultrathin films.In this paper, the following aspects will be discussed: (a) mechanical properties of ultrathin homopolymer and copolymer films, (b) dewetting dynamics of interfacially confined phase-separated homopolymers, and (c) the influence of graft-copolymers on the wetting and dewetting characteristics of homopolymers.
Monte Carlo Study of A+A+A→0 and A+2B→0 Reactions
Authors: Yen Andrew , Kopelman Raoul 
Published: April 2011

ABSTRACTThe diffusion-limited annihilation reactions A+A→products and A+B→products havebeen subject to theoretical, numerical, and experimental study over the past decade. “Anomalous” behaviors have been reported for both reactions, but with different upper critical dimensions (d=2 and d=4 respectively). The critical dimensions and the scaling of the exponents for the generalized reaction nA+mB→products depends on n and m. We present Monte Carlo simulations for two different types of third-order reactions, A+A+A→0 and A+2B→0, on both one and two dimensional lattices. Our numerical results show that for the two-dimensional case the behavior of the reaction follows mean-field theory while in one dimension the result is“anomalous”. Our numerical results are in good agreement with theory based on microscopic arguments and scaling analysis.
Line Tension Effect on Alkane Droplets Near the Wetting Transition
Authors: Dussaud A. D. , Vignes-Adler M. 
Published: April 2011

ABSTRACTWe have investigated n-octane droplets resting on the surface of sodium chloride solutions as a function of the salt concentration in a saturated, closed cell. For high salt concentration, the system approaches a wetting transition : the contact angles are very small (∼ 1°), the macroscopic droplet is unstable, and it breaks up spontaneously into microdroplets. The stable polydisperse population of microdroplets (5 μm < r < 250 μm) allowed us to analyze the dependence of the contact angle on droplet size. Because of the low contact angle values, accurate measurement ofcontact angles was obtained by interferometry. Moreover the accuracy of the classical method was significantly improved through the systematic use of three wavelengths. The relationship between the contact angle and the size droplet size indicated a positive line tension, τ, and the order of magnitude of τ was in good agreement with the theoretical prediction, τ, varies between (8.6 ± 0.9). 10−11 N and (1 ± 0.1).10−9 N and was dependent on the salt concentration. The positive sign of τ and its significant effect on droplet shape were related to the fact that the system was approaching the wetting transition.
Imaging Complex Fluids Under Confinement and Flow: Development of Bragg-Fresnel Optics for X-ray Microdiffraction
Authors: Li Youli , Idziak Stefan H.J. , Caine Ernie , Subramanian G. , Hu Evelyn , Safinya Cyrus R. 
Published: April 2011

ABSTRACTWe present results of simultaneous efforts to develop: 1.) Bragg-Fresnel Optics(BFO) to be used in X-ray microdiffraction methods, in particular as applied to structural studies of complex fluids and biomaterials under confinement and flow conditions; and 2.) Methodologies for confining complex fluids and biomaterials for in-situ structural studies. Using microelectronics process technology, we have fabricated linear and circular Bragg-Fresnel Lenses (BFL) in Si and III-V compound semiconductor substrates such as InP, GaAs and GaAs heterostructures with outermost zone width to 0.25 μm. X-ray characterization of linear BFLs were performed on a wiggler beamline at Stanford Synchrotron Radiation Laboratory (SSRL) at x-ray energies of 8 keV and 16 keV. A ∼5 μm focal spot size was obtained with a 50 μm incident beam, which was determined by the partial coherence of the source. On the confinement techniques, we have developed the X-ray Surface Force Apparatus (XSFA) which allows in-situ x-ray diffraction measurements to be made on fluid thin films confined between two atomically smooth surfaces. A new approach is being pursued to study the effects of confinement and flow on complex fluids and biological materials using microchannels fabricated on glass substrates.
Discontinuity in Particle Granular Temperature Observed in Gas Fluidized Beds Across The Geldart B/A Boundary - Implications for Stability and Properties of the Geldart A Phase
Authors: Cody George D. , Goldfarb David J. 
Published: April 2011

ABSTRACTWe present new experimental data on the properties of monodispersed glass spheresas a function of sphere diameter and gas flow in a gas fluidized bed. The data obtained by a novel non-intrusive probe of the average particle kinetic energy, or granular temperature, at thewall is used to explore and understand the well known empirical distinction between fluidized particles which exhibit a single phase state at initial fluidization (Geldart A powders) and fluidized particles that exhibit gas bubbles at initial fluidization (Geldart B powders). Specifically we show that the experimental “jump” we observe in the granular temperature atthe Geldart / transition is sufficient to account for the initial stability of the Geldart A phase on the basis of the one dimensional, first order, two wave, stability theory first introduced by Jackson in the early sixties. We present new data on the diameter dependent properties of the glass spheres during bed collapse and bed expansion, which demonstrate the distinctionbetween Geldart A and B behavior for these monodispersed glass spheres. Finally we present a simple Langevin model to account for the dependence of the granular temperature on sphere diameter and gas flow, and discuss the implications of these new experimental data for the fundamental physics of the Geldart A phase.
Numerical Simulation of the Transient Photoconductivity in A-SI:H as a Function of the Excitation Density
Authors: Feist H. , Kunst M. 
Published: April 2011

ABSTRACTThe dependence of the transient photoconductivity induced by pulsed excitation (TPC) on the excitation density is discussed with the help of numerical simulations. It is shown that recombination between excess mobile electrons and all excess holes (mainly localized) can explain the excitation density dependence of the TPC amplitude of standard a-Si:H at room temperature using a rate parameter kBB of 10−8cm3/s. This model leads to a decay faster than experimentally observed in the time range from 40ns to 1 μs. A variation of the recombination model is presented that gives a better fit for the longer time range still showing the correct excitation density dependence in the short time range. Moreover comparison of the simulations with experimental data yields limits for the parameters of the conduction band tail. In particular, the time necessary to establish a dynamic equilibrium of excess electrons between delocalized states in the conduction band and localized states in the tail appears to be very informative.
Optically Induced Conductivity Changes in Amorphous Silicon: A Historical Perspective
Authors: Staebler David L. 
Published: April 2011

ABSTRACTA historical perspective of the discovery of optically induced changes in amorphous silicon is presented in this paper from my personal point of view. It includes the story of how Chris Wronski and I discovered the effect, the key elements in our R&D environment that lead to our quick realization that the effect was reversible and reproducible, how our research environment supported the rapid publication of our first paper, and a brief look at the effect from today's perspective.
Pulsed-Laser Crystallized Highly Conductive boron-doped Microcrystalline Silicon
Authors: Nebel C. E. , Dahlheimer B. , Karrer U. , Stutzmann M. 
Published: April 2011

ABSTRACTThe preparation of seed lattices, using three interfering beams (TIB) from a pulsed Nd:YAG laser in a-Si layers of 100 to 400 nm thickness is introduced and applied for seeded laser or thermally induced crystallization of a-Si on Corning 7059 glass. The structural and electronic properties of the μc-Si layers are investigated by X-ray, electron- and atomic force microscopy, Hall and conductivity measurements. In highly boron-doped μc-Si, grains up to 1.3 μm in diameter are detected, giving rise ti conductivities of ≃ 2000 S/cm and hole mobilities of ≃ 10cm2/Vs.
Growth of Micro-Crystalline SI:H and (SI,GE):H on Polyimide Substrates using ECR Deposition Techniques
Authors: Erickson Karl , Dalal Vikram L. , Chumanov George 
Published: April 2011

ABSTRACTWe report on the growth of good quality micro-crystalline Si:H and (Si,Ge):H films on polyimide substrates using a remote plasma ECR deposition technique. We find that under conditions that lead to significant ion bombardment of the substrate, the films are microcrystalline even at relatively low deposition temperatures of about 250 C. A critical factor in inducing micro-crystallinity is the presence of a metal coating layer on polyimide. In the absence of such a coating, the films are amorphous, probably because the uncoated polyimide substrate charges up and prevents any further ion bombardment. The quality of the films was measured using both Raman spectroscopy and by studying the activation energy and low-energy absorption coefficient of the films. The sub gap absorption coefficient was found to follow the crystalline Si absorption curve quite well. The addition of germane to the gas phase shifted the absorption curve to smaller energies.
Laser Induced Melting and Crystallization of Boron Doped Amorphous Silicon
Authors: Nebel C. E. , Schöniger S. , Dahlheimer B. , Stutzmann M. 
Published: April 2011

ABSTRACTTransient reflectivity experiments have been performed to measure the dynamics of laser-induced melting of amorphous silicon (a-Si) and the crystallization to μ-Si of films with different thicknesses on Corning 7059 glass. The laser-induced melting takes place with a velocity of 13 to 24 m/s, while the solidification is about a factor 10 slower. The crystallization starts at the Si/glass interface and at the surface. In the center of the films, Si remains liquid for an extended period of time. The crystallization dynamics point towards an heterogeneous morphology of laser-crystallized Si, where the surface and the interface layers are composed of small grains and the bulk of larger grains.
Photoluminescence and Optical Characterization of a-SixN1-x:H based Multilayers Grown by PECVD
Authors: Giorgis F. , Giuliani F. , Pirri C. F. , Tresso E. , Galloni R. , Rizzoli R. , Summonte C. , Desalvo A. , Zignani F. , Rava P. , Cacca Vale F. 
Published: April 2011

ABSTRACTHigh room temperature photoluminescence efficiency (PLE) was observed for the first time in a-SixN1-x:H based nanometric multilayers deposited by plasma enhanced chemical vapour deposition (PECVD). The structure consists of alternate stoichiometric a-Si3N4:H barrier layers (E04=5.0 eV) and well layers in which E04 is varied between 2.11 eV and 2.64 eV. The peak of PL spectra and the absorption coefficient edge exhibits a blue shift up to 0.5–0.6 eV by decreasing the well thickness from 30 Å down to 5–10 Å. A strong increase in the PLE of multilayers, with well thickness around 5–10 Å, with respect to the PLE of bulk material was obtained.A p-i-n light emitting device (LED) with a multilayered structure as i-layer, having well layers with E04=2.64 eV and thickness 10 Å, is presented. The LED under forward bias shows an emission visible with the naked eye, with limited degradation after 8 hours of continuous operation.
Structure and Electronic Parameters of A-Si:H Deposited by DC-MASD
Authors: Golikova O. A. , Kuznetsov A. N. , Kudoyarova V. Kh. , Kazanin M. M. , Adriaenssens G. J. , Herremans H. 
Published: April 2011

ABSTRACTA systematic study of structure and electronic parameters of a-Si:H deposited by dc-magnetron assisted SiH4 decomposition (MASD) depending on substrate temperature, gas pressure, gas flow and grid mounting has been carried out. Correlation between the film microstructure, dangling bond density and electron mobility-life time product were established. The photoconductivity changes under light soaking were shown to be minimal when the films contained hydrogen in the (SiH2)n chains.
Preparation and Properties of Hydrogen Ated Amorphous Germanium Nitride a-GeNx:H
Authors: Hioki M. , Nitta S. , Takeda Y. , Yamamoto K. , Sasaki M. , Itoh T. , Nonomura S. 
Published: April 2011

ABSTRACTThe properties of a-GeNx:H films have been studied including the effects of oxygen and carbon impurities. The contamination of a-GeNx:H with oxygen and carbon is expressed as a-GeNx(OyCz):H, where x=N/Ge, y=O/Ge and z=C/Ge. The characteristics of a-GeNx(OyCz):H are summarized as follows: the sample is transparent at the center of a film, and the color of a film varies to light yellow and to brown at the outer edge depending on the magnetic field of the magnetron sputtering. The compositional ratios of the film vary from x=0.34 to 0.28, y=0.15 to 0.25 and z=0.05 to 0.02 at the center and at outer edge of a film, respectively. Optical gap energy EO5, obtained by the photon energy at optical absorption coefficient of 5×103 cm−1, are 2.9 eV at the center and 1.7 eV at the outer edge of a film. Eo5 increases with the nitrogen content x in a-GeNx(OyCz):H but is independent of the content of oxygen and carbon.
Structural Relaxation of Vacancies in Amorphous Silicon
Authors: Kim Eunja , Lee Young Hee , Chen Changfeng , Pang Tao 
Published: April 2011

ABSTRACTWe have studied the structural relaxation of vacancies in amorphous silicon (a-Si) using a tight-binding molecular-dynamics method. The most significant difference between vacancies in a-Si and those in crystalline silicon (c-Si) is that the deep gap states do not show up in a-Si. This difference is explained through the unusual behavior of the structural relaxation near the vacancies in a-Si, which enhances the sp2 + p bonding near the band edges. We have also observed that the vacancies do not migrate below 450 K although some of them can still be annihilated, particularly at high defect density due to large structural relaxation.
An AFM Study of The Effect of Growth Method and Conditions on The Microstructure of A-Si:H
Authors: Kwon Daewon , David Cohen J. , Garcia Ricardo 
Published: April 2011

ABSTRACTWe utilized atomic force microscopy (AFM) to investigate the microstructure at the surface of thick (>4000 Å) hydrogenated amorphous silicon films. The films were prepared by standard glow discharge (GD) as well as hot wire chemical vapor deposition (HWCVD) techniques. We studied a series of films with substrate temperatures ranging between 200 °C and 400 °C. We also studied the effects of various gas mixtures at fixed growth temperature on the observed microstructure. We found that the average feature grain size in the micro structure varied between 40 nm and 90 nm as the substrate temperature was changed and also as the different gas mixtures were employed during growth. The grain size decreased with increasing substrate temperatures for the films grown from 100 % silane independent of whether the growth method were GD or HWCVD. Gas dilution with argon or hydrogen also resulted in a size reduction, as did PH3 doping at dilute levels. These results rule out the possibilities that the observed features arise from particle production in the reactor chamber itself. The relation of the observed micro structure to the electronic properties of a-Si:H is discussed.
In-Situ Monitoring of Surface Hydrogen on the a-SiGe:H Films
Authors: Toyoshima Y. , Ganguly G. , Ikeda T. , Saitoh K. , Kondo M. , Matsuda A. 
Published: April 2011

ABSTRACTThe bonded hydrogen on the growing surface of hydrogenated amorphous silicon germanium (a-SiGe:H) alloy films has been investigated by use of infrared reflection absorption spectroscopy (IR-RAS). When the alloy films are Si-rich, the surface hydrogen bonded to Si atoms is found to behave in a similar way to those on the hydrogenated amorphous silicon (a-Si:H) films. This means that the thermal desorption stability of surface Si hydride species is not significantly affected by the coexistence of a small amount (typically 20 at.%) of Ge. On the contrary, the desorption behavior of surface hydrogen depends on the alloy composition when the a-SiGe:H films are Ge-rich. A surface reaction scheme is provided in an attempt to explain this series of behavior in surface hydrogen on the a-SiGe:H films.
Light-Induced Metastable Defects or Light-Induced Metastable H Atoms in a-Si:H Films?
Authors: Godet C. 
Published: April 2011

ABSTRACTIn hydrogenated amorphous silicon (a-Si:H) films, the increase of the metastable defect density under high-intensity illumination is usually described by an empirical two-parameter stretched-exponential time dependence (characteristic time τSE and dispersion parameter β). In this study, a clearly different (one-parameter) analytic function is obtained from a microscopic model based on the formation of metastable H (MSH) atoms in a-Si:H films. Assuming that MSH atoms are the only mobile species, only three chemical reactions are significant : MSH are produced from doubly hydrogenated (SiH HSi) configurations and trapped either at broken bonds or Si-H bonds, corresponding respectively to light-induced annealing (LIA) and light-induced creation (LIC) of defects. Competition between trapping sites results in a saturation of N(t) at a steady-state value Nss. A one-parameter fit of this analytical function to experimental data is generally good, indicating that the use of a statistical distribution of trap energies is not necessary.
Evidence of Hysteresis in a New p-i-n-i-p-i-n Amorphous Silicon Device
Authors: Caputo D. , De Cesare G. , Palma F. 
Published: April 2011

ABSTRACTA novel device based on a-Si:H p+-i-n−-i-p−-i-n+ structure, showing a hysteresis in its current-voltage curve is reported. A numerical device model allows to investigate in detail the fundamental role of the two lightly doped n− and p− layers, where charge trapping determines the bistable behavior of the device. The ON condition is mantained until the ambipolar charge injection overcomes the fixed charge. The transition OFF-ON starts when, increasing the applied voltage, one of the two lightly doped layers becomes completely depleted. The transition ON-OFF is, instead, mainly dependent on the recombination processes occurring in the central doped layers. Devices with hysteresis around 2 V and tum-on voltage around 12 are presented.