bluuebunny/crossref_metadata_2025_split huggingface dataset:
New Advances in Molding and Printing Processes for Organic/Plastic Electronics Using Chemically Modified Stiff, Photocured Poly (dimethylsiloxane) (PDMS) Elastomers Designed for Nano-Resolution Soft Lithography
Authors: Choi Kyung M. , Rogers John A. 
Published: April 2011

ABSTRACTThe development of new materials for organic/plastic electronics allows us to fabricate novel devices through unconventional approaches. The ‘soft lithography technique’ has been widely used in replicating and fabricating small features. This technique is a low cost alternative to photolithography by generating structures from masters to substrates, which employ ‘elastomeric materials’, such as highly stretchable silicon elastomer, polydimethylsiloxane (PDMS) to replicate or transfer the original features to a variety of substrates by molding and printing processes. Since the resolution of pattern transfer significantly relies on the performance of polydimethylsiloxane (PDMS) stamp materials, commercial PDMS materials have shown limitations in high fidelity pattern transfer due to their low physical toughness and high thermal expansion coefficients. For those reasons, pattern fabrications using conventional PDMS materials are unable to satisfy our set of diverse demands, especially in the area of nano-scale replication. To achieve high performance in molding and printing, here we introduce a new strategy, design and synthesis of a modified PDMS silicon elastomer that is a stiffer and photocurable element to achieve our specific task of nano-scale resolution soft lithography. We then demonstrated its unique capabilities for the case of nano-features (300 nm wide) with narrow and tall heights (600 nm height) of photoresist, which is one of the most challenging ‘nano-patterning’ tasks in advanced soft lithography, which is often limited in its use at the nano-scale with other commercially available elastomers.
Control of Current Reversal and Separation of Particles in Inertia Ratchets
Authors: Family F. , Larrondo H.A. , Arizmendi C.M. 
Published: April 2011

ABSTRACTWe have studied the deterministic dynamics of underdamped single and multiparticle ratchets associated with current reversal, as a function of both the amplitude and the frequency of an external driving force. We show that control of current reversals in deterministic inertia ratchets is possible as a consequence of a locking process associated with different mean velocity attractors. Control processes employing small perturbations on the frequency and the amplitude of the external force may be designed in view of the intermixed fractal nature of the domains of attraction of the mean velocity attractors. The range where each control parameter is capable of reversing the current is determined. Quenched noise has significant effect on the basins of attraction. In particular, with increasing disorder the direction of a packet of particles can be reversed, leading to disappearance or weakening of the negative velocity attractor. The influence of the mass of the particles is also considered in order to design control techniques capable of separating particles of different masses.
Molecular pumping and separation in a symmetric channel
Authors: Fleishman D. , Filippov A.E. , Urbakh M. 
Published: April 2011

ABSTRACTA mechanism responsible for directed transport and molecular separation in asymmetricchannel is proposed. We found that under the action of spatial harmonic oscillations of the channel, the system exhibits a directed transport in either direction, presenting multiple current reversals as the amplitude and/or frequency of the oscillations are varied. The particles of different masses may be forced to move with different velocities in the same or in the opposite directions by properly adjusting driving parameters. The directed transport can be produced in both directions even in the absence of thermal noise, the latter can speed up or slow down the transport depending on the system parameters.
Bimodal Structured Bulk Nanocrystalline Al-7.5Mg Alloy
Authors: Lee Zonghoon , Witkin David B. , Lavernia Enrique J. , Nutt Steven R. 
Published: April 2011

ABSTRACTThe microstructure, mechanical properties and deformation of bimodal structured nanocrystalline Al-7.5Mg alloy were investigated. Grain refinement was achieved by cryomilling of atomized Al-7.5Mg powders, and then cryomilled nanocrystalline powders blended with 15% and 30% unmilled coarse-grained powders were consolidated by hot isostatic pressing followed by extrusion to produce bulk nanocrystalline alloys. Bimodal bulk nanocrystalline Al-7.5Mg alloys, which were comprised of nanocrystalline grains separated by coarse-grain regions, show balanced mechanical properties of enhanced yield and ultimate strength and reasonable ductility and toughness compared to comparable conventional alloys and nanocrystalline metals.
Mechanical Properties of a Cryomilled Nanostructured Al-Mg Alloy
Authors: Han B. Q. , Mohamed F. A. , Bampton C. , Lavernia E. J. 
Published: April 2011

ABSTRACTThe microstructural characteristics and mechanical behavior at room temperature of a nanostructured Al-Mg alloy, with grain sizes of approximately 100 nm, manufactured by a cryomilling process were investigated in the present study. The results reveal an asymmetry of yield strength between tension and compression. On the basis of the mechanical behavior results it appears that the presence of a few micron inclusions may have a negative effect on tensile behavior of the cryomilled nanostructured Al-Mg alloy.
Dislocation Confinement and Ultimate Strength in Nanoscale Metallic Multilayers
Authors: Li Qizhen , Anderson Peter M. 
Published: April 2011

ABSTRACTIn nanostructured metallic multilayers, hardness and strength are greatly enhanced compared to their microstructured counterparts. As layer thickness is decreased, three different regions are frequently observed: the first region shows Hall-Petch behavior; the second region shows an even greater dependence on layer thickness; and the third region exhibits a plateau or softening of hardness and strength. The second and third regions are studied using our discrete dislocation simulation method. This method includes the effects of stress due to lattice mismatch, misfit dislocation substructure, and applied stress on multilayer strength. To do so, we study the propagation of existing threading and interfacial dislocations as the applied stress is increased to the macroyield point. Our results show that in region 2, dislocation propagation is confined to individual layers initially. This “confined layer slip” builds up interfacial content and redistributes stress so that ultimately, the structure can no longer confine slip. The associated macroyield stress in this region depends strongly on layer thickness. In region 3, layers are so thin that confined layer slip is not possible and the macroyield stress reaches a plateau that is independent of layer thickness.
Plastic Deformation and the Role of Fault Formation in the Equation of State of Micron Size Intermetallic Alloys Under Non-Hydrostatic Pressure
Authors: Vassiliou John K. , Otto J. W. , Frommeyer G. , Davis J. J. , Pinto P. 
Published: April 2011

ABSTRACTThe elastic and plastic deformation of micron size anisotropic polycrystals of Ni3Al and Cu3Au intermetallic alloys have been studied under non-hydrostatic conditions by energy-dispersive X-ray diffraction (EDX) in a diamond-anvil cell. Compression was achieved by confining the samples in a viscous fluid or directly between the diamond anvils. Deviatoric forces are introduced in the samples as a result of the increasing viscosity with pressure and the eventual glassification of the pressurizing medium or by the contact forces of the diamond anvils. Line shifts and line profiles were used to analyze elastic and plastic strains. Plastic deformation is due to the onset of non-hydrostatic stresses and the introduction of stacking faults and dislocations. A volume incompressibility due to plastic deformation and the saturation of the stacking fault probability is followed by an elastic compression of a fully plastically deformed state. The compression of this state is isotropic and independent of the presence and type of the pressurizing medium. From the measured strains at different crystallographic orientations, the uniaxial stress and the stacking fault probability as a function of the confining pressure are derived and their role in the equation of state is examined. Using finite elasticity, the equation of state is derived in the presence of uniaxial stresses causing stacking faults, defects and dislocations.
Defect diffusion in hcp Zirconium: A kinetic Monte Carlo approach
Authors: Arévalo C. , Caturla M.J. , Perlado J.M. 
Published: April 2011

ABSTRACTWe have studied diffusion of defects produced during irradiation in hcp zirconium through a kinetic Monte Carlo model. The input data for these simulations is based on molecular dynamics calculations and from experiments whenever available. The initial cascade damage produced by recoils of 25 keV energy from molecular dynamics simulations has been followed for times of hours at a fixed temperature of 600K. We have calculated the number of freely migrating defects, the recombination ratio between vacancies and interstitials, the defects surviving in the bulk as well as the average cluster size for these remaining defects.
Localized Charging Effects Resulting From Focused Ion Beam Processing Of Non-Conductive Materials
Authors: Stevens-Kalceff Marion. A. , Rubanov S. , Munroe P. R. 
Published: April 2011

ABSTRACTFocused Ion Beam (FIB) systems employ a finely focussed beam of positively charged ions to process materials. Ion induced charging effects in non-conductive materials have been confirmed using Scanning Surface Potential Microscopy (SSPM). Significant localized residual charging is observed within the ion implanted micro-volumes of non-conductive materials both prior to and following the onset of sputtering. Characteristic observed surface potentials associated with the resultant charging have been modelled, giving insight into the charging processes during implantation and sputtering. The results of this work have implications for the processing and microanalysis of non-conductive materials in FIB systems.
Molecular Dynamics Study Of Surface Morphological Evolution By Cluster Impacts
Authors: Aoki Takaaki , Matsuo Jiro , Yamada Isao 
Published: April 2011

ABSTRACTIn order to understand the characteristics of surface modification process with cluster ion irradiation, molecular dynamics simulations of Ar cluster impacting on Si surface with various surface structures were carried out. It was found that the surface morphology is dynamically deformed with only one cluster impact and the impact process of cluster is different depending on the local surface structure. For example, when an Ar2000 cluster accelerated with 20keV impacted on the convex point of the surface, the hill was compressed and the impact area was smoothed. At the impact on a concave point, a deeper crater was formed compared with the impact on a flat surface. On the other hand, the MD simulations of sequential impacts of large clusters were performed. It was found that the small tip structures on the surface could be removed easily with cluster irradiation. It was shown that surface roughness converges to 15∼20Å and this value agrees with the result obtained by single impact of cluster.
He+ ion damage in 4H-SiC studied by charge collection efficiency measurements.
Authors: Nipoti Roberta , Donolato Cesare 
Published: April 2011

ABSTRACTThe nuclear microprobe facility of the Italian National Laboratories of Legnaro was used for an Ion Beam Induced Charge Collection (IBIC or IBICC) experiment which measured the charge collection of a 4H-SiC Schottky diode irradiated with 2 MeV He+ at increasing doses. The experiment was arranged so as to obtain a statistics of about 1400 events per each He+ ion from the 1st to the 500th one on the ion microprobe spot (1.5 × 1.5 μm2). These figures correspond to He+ fluence values in the range 107−1011 ions/cm2. The charge collection of the diode was almost constant from the 1st to the 10th He+ ion, i.e. up to a fluence of 109 ions/cm2, and then monotonically decreased for the subsequent ions. The SiC device collection efficiency was modelled by representing the electrical effects of the damage produced by ions as a planar interface region of given carrier recombination velocity at the depth of the damage peak. Experimental and computed data scale one to the other assuming that the interface recombination velocity and He+ fluence are linearly related.
Fabrication of Nanotips and Microbeams in Antimonide Based Semiconductor Material using Bromine Ion Beam Assisted Etching
Authors: Krejca B. , Vangala S.R. , Krishnaswami K. , Kolluru R. , Ospina M. C. , Sung C. , Goodhue W. D. 
Published: April 2011

ABSTRACTAntimonide-based compound semiconductors have emerged as the materials of choice for fabricating high-speed low-power electronics and electro-optics for applications requiring miniaturization and portability. In this work Br-IBAE is shown to be an anisotropic antimonide etching technique that is capable of generating novel structures as well as performing standard etching tasks. When etching less than optimally chemical-mechanical polished (111) InSb wafers, sharp-tipped cone structures with tip radii of the order of less than 60 nm are produced. These structures may be ideally suited for the development of field-emission devices, where small tip radii are required for useful emission currents. The anisotropic nature of the IBAE technique allows one to etch channels in the surface at angles up to 70° from perpendicular, making the fabrication of microbeams feasible. Using an angled sample holder, the first etch undercuts the masked beams from one side. The sample is then removed and realigned so as to undercut the beams from the other side. The triangular shaped microbeams are left suspended from either one or both ends. Using a combination of atomic force microscopy and mechanical engineering beam analysis techniques, the elastic parameters of the material can be measured. The microbeams can be aligned along various directions on the surface to investigate anisotropic characteristics. This is particularly important for determining the mechanical characteristics of materials that can only be grown in thin epitaxial layers, such as quaternary antimonide-based compound semiconductors.
Formation of High Quality β-FeSi2 by Pre-Amorphization-Enhanced Diffusion
Authors: Murakami Y. , Kenjo A. , Sadoh T. , Yoshitake T. , Miyao M. 
Published: April 2011

ABSTRACTEffects of Ar+ ion irradiation on solid-phase growth of β-FeSi2 have been investigated. Si substrates were amorphized with Ar+ ions (20 keV) before Fe (15 nm) deposition to form Fe(15 nm)/a-Si/c-Si stacked structures. As a reference, Fe/c-Si stacked structures were prepared. In the initial stage of annealing at 800 °C, β-FeSi2 formation was enhanced for pre-amorphized samples, which was due to the enhanced diffusion of silicidation species. In the long time annealing, β-FeSi2 formation proceeded by thermal equilibrium diffusion, and the formation rate was not affected by pre-amorphization. Crystal quality of β-FeSi2 was improved by pre-amorphization. The pre-amorphization enhanced diffusion is useful for formation of high quality β-FeSi2 thin films.
Preamorphization-induced defects in shallow P+N junctions characterized by an ac magnetic field
Authors: Abdelaoui M. , Mehor H. , Idrissi M. , Benzohra M. , Olivié F. 
Published: April 2011

ABSTRACTGermanium implantation into silicon substrate is currently used to preamorphisize the crystalline structure in order to avoid boron channeling effects in shallow P+N junction manufacturing. Nevertheless, after boron doping and rapid thermal annealing, different defects are formed within the structure, such as end of range defects which are created at the amorphous/crystalline interface. Our study concerns two types of shallow P+N junctions. These junctions were fabricated using low energy boron implantation at 3 KeV with a dose of 2×1015 cm-2 into high-energy germanium preamorphized n-type crystalline silicon substrates at 2.2 MeV with a dose of 1015 cm-2. In the first type, the preamorphization was performed at ambient temperature. In the second, the preamorphization was performed at liquid nitrogen temperature. Boron doping was followed by a Rapid Thermal Annealing (RTA) step for 15 s at 950 °C. Deep Level Transient Spectroscopy (DLTS) technique was used to characterize the defects formed in each structure. The impact of an ac magnetic field on the reverse current has been studied at a given bias, when sweeping the sample temperature. The measurements were performed under a low frequency (less than 1 kHz) magnetic field of a Vrms value of 2000 G, with sample temperature varying between 80 and 260 K. The results show a high activity of defects at low frequencies (1 and 10 Hz) for the nitrogen preamorphized sample. Moreover, this activity is observed at about 200 K which corresponds to the peak of the DLTS spectra of such sample. However, the ambient preamorphized sample characterized by a lower concentration of defects seems to be insensitive to the ac magnetic field. Therefore, it appears that the preamorphization-induced defects influence strongly the response of the junction to an applied ac magnetic field.
Ge Nanocrystal Formed Directly by High-Dose-Ion-Implantation and the Related UV-VIS Photoluminescence
Authors: Zeng Yingqiu , Lu Tiecheng , Zou Ping , Zhu Sha , Wang Lumin , Shen Liru 
Published: April 2011

ABSTRACTThe investigation of nanocrystalline Ge (nc-Ge) directly prepared with high dose Ge ion implantation of 1×1016, 1×1017, 5×1017and 1×1018cm-2respectively without subsequent annealing is presented in this paper. The specimens were measured by means of GIXRD, LRS and PL. The results show the nc-Ge, which possesses strong compressive stress, can be fabricated when the implanting dose of Ge ions is over the threshold dose∼1×1017cm-2. The content and size of nc-Ge will enlarge with increasing dose. The nc-Ge formation mechanism may be the Ge atoms in the amorphous Ge (a-Ge) clusters, which are formed through the aggregation of implanted Ge ions, obtain energy from the instant local annealing zone induced by the incident Ge ion and reconstruct to nc-Ge existing in a-Ge clusters. The PL results indicate the strong PL peaks centered at about 295, 400 and 570 nm can be observed in implanted samples. The intensity of these PL peaks increases with increasing dose. The related PL mechanism in Ge-ion-implanted SiO2film has also been discussed.
Facile Fabrication of Nanoparticles in the Nanospace of Ultrathin TiO2-Gel Films: Composition, Morphology and Catalytic Activity
Authors: He Junhui , Kunitake Toyoki 
Published: April 2011

ABSTRACTIn this article, we present in-situ synthesis of nanoparticles of various compositions and morphologies in the nanospace of ultrathin TiO2-gel films using low temperature H2 and O2 plasmas as reductant and oxidant, respectively. Parameters that influence the formation of nanoparticles were investigated and discussed. Reversible chemical transformation was found to give monodisperse nanoparticles. Catalytic activities of Pd monometallic and Ag-core/Pd-shell bimetallic nanoparticles were tested for hydrogenation of methyl acrylate. The much enhanced catalytic activity is attributed mainly to a large ratio of the surface Pd atoms.
Size and critical thickness evolution during growth of stacked layers of InAs/InP(001) quantum wires studied by in situ stress measurements
Authors: Fuster David , González María Ujué , González Luisa , González Yolanda , Ben Teresa , Ponce Arturo , Molina Sergio I. 
Published: April 2011

ABSTRACTSize and spatial distribution homogeneity of nanostructures is greatly improved by making stacks of nanostructures separated by thin spacers. In this work we present in situ and in real time stress measurements and reflection high energy electron diffraction (RHEED) observations and ex situ transmission electron microscopy (TEM) characterization of stacked layers of InAs quantum wires (QWr) separated by InP spacer layers, d(InP), of thickness between 3 and 20 nm. For d(InP) < 20 nm, the amount of InAs involved in the newly created QWr from the 2nd stack layer on, exceeds that provided by the In cell. Our results suggest that in those cases InAs 3D islands formation starts at the P/As switching and lasts during further InAs deposition. We propose an explanation for this process that is strongly supported on TEM observations. The results obtained in this work imply that concepts like the existence of a critical thickness for 2D-3D growth mode transition should be revised in correlated QWr stacks of layers.
Optical properties of InGaAs QDs grown in a GaAs matrix by MOCVD, emitting at 1300 nm at room temperature
Authors: Todaro M. T. , De Giorgi M. , Tasco V. , De Vittorio M. , Passaseo A. , Cingolani R. 
Published: April 2011

ABSTRACTWe investigate the optical properties of InGaAs QDs emitting at 1330 nm, directly grown by Metal Organic Chemical Vapor Deposition (MOCVD) in a GaAs matrix, without indium in the barrier. The PL characterization of this new kind of QDs, shows very narrow lineshape at room temperature and a strong reduction of the temperature dependent quenching of the emission (a factor of 3 from 30 K to 300 K).The quantum external efficiency obtained by inserting such QDs into light emitting diode structures, despite the low dot density (1.6*109 cm−2), is 0.03%. This value corresponds to an individual QD efficiency about 30% higher than that reported in the literature for state of art InGaAs/InGaAs QD LEDs.
2-D Photonic Quasicrystal in Metallic Microcavity
Authors: Zhang J. Y. , Tam H. L. , Wong W. H. , Pun Y. B. , Xia J. B. , Cheah K. W. 
Published: April 2011

ABSTRACTPhotonic microcavity promises to be one of the photonic devices that can have immediate applications such as super bright LED and low threshold laser. Most photonic crystal structures currently used on microcavity are cubic or hexagonal, whose folding symmetry is no greater than 6. In this work, we fabricated 2-D photonic microcavity with Penrose quasicrystal pattern and measured the angular resolved transmission and photoluminescence spectra of the microcacity. From the experimental result it is found that isotropic photonic band gap exists in the microcavity with the Penrose quasicrystal pattern.
Design and Fabrication of Dispersion Controlled and Polarization Maintaining Photonic Crystal Fibers for Optical Communications Systems
Authors: Kawanishi Satoki , Yamamoto Takashi , Kubota Hirokazu , Tanaka Masatoshi , Yamaguchi Syun-ichiro 
Published: April 2011

ABSTRACTRecent progress on photonic crystal fibers (PCFs) is reviewed aiming at their application to high performance optical communications sytems. The optical properties, for example dispersion characteristics, can be set by selecting the appropriate combination of air hole diameter and air hole pitch. A noteworthy characteristic of PCFs is their strong birefringence, which suggests optical components with better polarization maintaining characteristics.This paper describes the characteristics of dispersion controlled PCFs and polarization maintaining PCFs. It describes theoretical analyses and experimental results of fabricated PCFs that have short wavelength zero dispersion at 810 nm, polarization maintaining capability with birefringence of 1 × 10−3, polarization maintaining dispersion flattened functions, and absolute single polarization state support with polarization dependent loss of 1 dB/m at 1550 nm. A supercontinuum generation experiment with PM-PCF in the 1550 nm region is shown with symmetrical spectral broadening to over 40 nm. The potential of PCFs will be discussed with reference to the next generation optical communications systems.