bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fabrication and Imaging of Protein Crossover Structures
Authors: LaGraff John R. , Zhao Yi-Ping , Graber David J. , Rainville Dan , Wang Gwo-Ching , Lu Toh-Ming , Chu-LaGraff Quynh , Szarowski Don , Shain William , Turner James N. 
Published: April 2011

ABSTRACTProteins often deform, dehydrate or otherwise denature when adsorbed or patterned directly onto an inorganic substrate, thus losing specificity and biofunctionality. One method used to maintain function is to pattern the protein of interest directly onto another underlying protein or polypeptide that acts as a buffer layer between the substrate and the desired protein. We have used microcontact printing (μcp) to cross-stamp orthogonal linear arrays of two different proteins (e.g., IgG, poly-lysine, protein A) onto glass substrates. This created three separate types of protein-substrate microenvironments, including crossover structures of protein one on protein two. We report preliminary fluorescent microscopy and scanning force microscopy characterization of these structures, including commonly encountered structural defects.
Development of Polyimide-based Flexible Tactile Sensing Skin
Authors: Engel Jonathan , Chen Jack , Liu Chang , Flachsbart Bruce R. , Selby John C. , Shannon Mark A. 
Published: April 2011

ABSTRACTWe present a novel microfabrication process for realizing a new type of flexible sensory “smart skin”. In this work, we focus on demonstration of a skin containing a two dimensional array of tactile sensors using polyimide and metal strain gauges. A novel polymer microfabrication approach coupled with surface release methods is demonstrated. The process yields flexible sensory skins in a low cost, efficient manner. Experimental characterization of the devices is also presented. The demonstrated sensors use metal-film strain gauges in a multiplexed two-dimensional array of tactile pixels (taxels) embedded in a polyimide thin film membrane to detect force distribution on the flexible skin. The arrays have been used to image force distributions and could be used with slip-detection friction measurement for robotic gripping application.
High Performance Organic Field Effect Transistor Withanovel Top-And-Bottom Contact (TBC) Structure
Authors: Yoshida Manabu , Uemura Sei , Hoshino Satoshi , Kodzasa Takehito , Haraichi Satoshi , Kamata Toshihide 
Published: April 2011

ABSTRACTWe studied the features of the newly developed Top and Bottom Contact Field Effect Transistor (TBCFET) with organic semiconductor layers. TBCFETs with ca.0.5μm channel length (L) were fabricated and their transistor properties were measured. The output drain-source currents (IDS) of TBCFET were 1 to 2 orders of magnitude higher than those of ordinary planar type FETs with 100μm channel length. On the other hand, because of the TBC structure, off current tends to become larger in the TBCFET. Therefore, in order to solve this off-current problem, we intentionally formed the Schottky junction at the top electrode/semiconductor interface. As a result, the off current became about 2 orders of magnitude smaller than before the formation of the Schottky junction.
Tunnel-Coupled Quantum Dots: Atomistic Theory of Quantum Dot Molecules and Arrays
Authors: Bryant Garnett W. , Aizpurua Javier , Jaskolski W. , Zielinski Michal 
Published: April 2011

ABSTRACTAn understanding of how dots couple in quantum dot molecules and arrays is needed so that the possibilities for tailored nanooptics in these systems can be explored. The properties of tunnel-coupled dots will be determined by how the dots couple through atomic-scale junctions. We present an atomistic empirical tight-binding theory of coupled, CdS nanocrystal artificial-molecules, vertically and laterally coupled InAs/GaAs self-assembled dots, and arrays of InAs/GaAs self-assembled dots. Electron states follow the artificial molecule analogy. The coupling of hole states is much more complex. There are significant departures from the artificial molecule analogy because the interdot hole coupling is determined by the hole envelope functions, as for the electron states, and by the hole atomic state near interdot interfaces.
Charged Excitons in Self-assembled Quantum Dots
Authors: Warburton R. J. , Urbaszek B. , McGhee E. J. , Schulhauser C. , Högele A. , Karrai K. , Govorov A. O. , Garcia J. M. , Gerardot B. D. , Petroff P. M. 
Published: April 2011

ABSTRACTWe have succeeded in generating highly charged excitons in InAs self-assembled quantum dots by embedding the dots in a field-effect heterostructure. We discover an excitonic Coulomb blockage: over large regions of gate voltage, the exciton charge remains constant. We present here a summary of the emission properties of the charged excitons.
Shape Engineered InAs Quantum Dots with Stabilized Electronic Properties
Authors: Tokranov V. , Yakimov M. , Katsnelson A. , Dovidenko K. , Lamberti M. , Oktyabrsky S. 
Published: April 2011

ABSTRACTWe have studied the influence of overgrowth procedure and a few monolayer-thick AlAs overlayer on the properties of self-assembled InAs quantum dots (QDs) using scanning electron microscopy (SEM) and photoluminescence (PL). PL spectroscopy was used to optimize optical properties of the QDs by shape engineering (QD truncation) through adjustment of the thickness of overlayers and temperature of the subsequent heating. QDs with 6 nm - thick overlayer with subsequent heating up to 560°C was found to have the highest PL intensity at room temperature and the lowest FWHM, 29 meV. Ground state energy of the truncated QDs is very stable against variations of growth parameters. 1.23 μm edge-emitting laser of triple-layer QD structure demonstrated room temperature threshold current density, 74 A/cm2.
Silicon Epitaxial Regrowth Passivation of SiGe Nanostructures Pattered by AFM Oxidation
Authors: Bo Xiang-Zheng , Rokhinson Leonid P. , Sturm J. C. 
Published: April 2011

ABSTRACTSiGe quantum devices were demonstrated by AFM oxidation and selective wet etching with features size down to 50 nm. To passivate the devices and eliminate the interface states between Si/SiO2, low temperature regrowth of epitaxial silicon over strained SiGe has been tested. The silicon regrowth on Si0.8Ge0.2 was done by rapid thermal chemical vapor deposition (RTCVD) at 700 °C using a hydrogen pre-cleaning process at 800 °C and 10 torr. SIMS analysis and photoluminescence (PL) of strained SiGe capped with epitaxial regrown silicon show a clean interface. Nano-gaps between doped SiGe filled and overgrown with epitaxial silicon show an electrical insulating property at 4.2 K.
Wavelength Selective Charge Storage in self-assembled InGaAs-GaAs Quantum Dots
Authors: Kroutvar M. , Ducommun Y. , Finley J. J. , Bichler M. , Abstreiter G. , Zrenner A. 
Published: April 2011

ABSTRACTWe present the first demonstration of spectrally selective charge storage in self-assembled quantum dots that utilizes optical charge generation and readout of the stored charge distribution. Resonant optical excitation charges only a sub-ensemble of the inhomogeneous broadened dots. The optical readout process directly recovers the spectral distribution of stored charges. Wavelength selectivity is demonstrated in a two-color experiment exhibiting charge storage in two independent QD sub-ensembles. Resonant charge storage is observed at least up to 85K depending on excitation energy. Lack of time evolution of the spectral emission indicates charge storage times Δt much longer than 25μs.
Synthesis of Crystalline Silicon Nanoparticles in Low-Pressure Inductive Plasmas
Authors: Bapat Ameya , Kortshagen Uwe , Campbell Stephen A. , Perrey Christopher R. , Barry Carter C. 
Published: April 2011

ABSTRACTAmorphous silicon has been used for a wide variety of electronic applications including thin film transistors and energy conversion devices. However, these devices suffer greatly from defect scattering and recombination. A method for depositing crystalline silicon would be highly desirable, especially if it can be remotely created and deposited on any kind of substrate. Our work aims at synthesis and deposition of mono-disperse, single crystal silicon nanoparticles, several tens of nm in diameter on varied substrates. Synthesis of nanocrystals of 2–10 nm diameter has been previously reported but larger particles were amorphous or polycrystalline. This work reports the use of an inductively coupled low-pressure plasma to produce nanocrystals with diameters between 20–80 nm. Electron microscopy studies confirm that the nanocrystals are highly oriented diamond-cubic silicon.
Raman Analysis of Carbon Nanotube Bundles for Bio-electronic Applications
Authors: Chou Shin. G. , Dresselhaus Mildred. S. , Humphreys Elen , Chung Sung Yoon , VanderSande John , Chiang Yet Ming , Swan A. K. , Ünlü M. S. , Goldberg B. B. 
Published: April 2011

ABSTRACTThree different types of carbon nanotubes being considered for bio-recognition experiments were studied using resonance Raman spectroscopy. Raman spectroscopy, taken using several laser excitation energies, has been shown to provide an effective characterization tool for these carbon nanotubes. The technique yields structural information that both complements and corroborates structural information obtained using electron microscopy techniques, such as TEM, SEM, and AFM.
Carbon Nanotubes Grown on Metallic Wires by Cold Plasma Technique
Authors: Sarangi D. , Karimi A. 
Published: April 2011

ABSTRACTCarbon nanotubes on metallic wires may be act as electrode for the field emission (FE) luminescent devices. Growing nanotubes on metallic wires with controlled density, length and alignment are challenging issues for this kind of devices. We, in the present investigation grow carbon nanotubes directly on the metal wires by a powerful but simple technique. A novel approach has been proposed to align nanotubes during growth. Methane, acetylene and dimethylamine have been used as source gases. With the same growth conditions (viz. pressure, growth temperature and plasma) methane does not produce any nanotube but nanotubes grown with dimethylamine show shorter length and radius than acetylene. The effect of temperature to control the radius, time to control the density, plasma conditions to align the nanotubes has been focused. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Rutherford Back Scattering (RBS) are used to characterize the nanotubes.
Electron Irradiation on Amorphous Silicon
Authors: Cheng Ju-Yin , Murray J. 
Published: April 2011

ABSTRACTFor the first time we use fluctuation electron microscopy to study the effect of electron irradiation on amorphous silicon. Before showing the results, we compare two variable coherence methods, hollow cone and dark field. These techniques have been successfully implemented in the Philips CM12, JEOL 4000 and Hitachi 9000 microscopes. The image fluctuations for ion-implanted and vacuum-deposited amorphous silicon can be reliably measured under the conditions used in these microscopes.
Self-Organized ZnO Nanosize Islands with Low-Dimensional Characteristics on SiO2/Si Substrates by Metalorganic Chemical Vapor Deposition
Authors: Kim Sang-Woo , Fujita Shizuo , Fujita Shigeo 
Published: April 2011

ABSTRACTSelf-organized ZnO nanosize islands on thermally grown SiO2 layers on Si (111) with low-dimensional quantum characteristics were realized by metalorganic chemical vapor deposition. Investigation by atomic force microscopy showed that the density and size of the ZnO nanosize islands were changed by the growth conditions. In macroscopic photoluminescence measurements at 10 K using a 325 nm He-Cd laser, we observed the broad spectra with band tails, which were located at the higher energy with respect to band edge emission of ZnO thin films with the free exciton emission located at about 3.38 eV. These results indicate that these ZnO nanosize islands have low-dimensional quantum effect characteristics.
Phase Transitions in Octanethiol-Capped Ag, Au and CdS Nanocluster Assemblies
Authors: Ellis A. V. , Vijayamohanan K. , Ryu C. , Ramanath G. 
Published: April 2011

ABSTRACTWe describe phase transitions in assemblies of octanethiol (OT)-capped nanoclusters of Ag and Au and CdS of sizes ranging from 2 to 5 nm, created by a new variant of the Brust synthesis method, without the use of phase transfer agents. We probed the stability of these assemblies by a combination of UV-Visible spectrometry, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and in situ polarized microscopy (PLM). Our results show that Ag nanoclusters form a crystalline assembly at ambient temperatures. Upon heating, these assemblies undergo two reversible phase transitions corresponding to melting of (i) a phase comprised of excess thiols that are not linked to the nanoclusters, and (ii) the nanocluster assembly, at ∼60 and 124 °C, respectively. In contrast, Au nanocluster assemblies are softer, waxy solids, and show sub-zero melting transitions. Both these assemblies show no observable mass loss up to ∼180 °C. Cds nanocluster assemblies are also waxy solids, but show a nonreversible melting transition at 137 °C, with simultaneous mass loss due to OT desorption. From our results the thermal stability of the nanoclusters was OT-Ag > OT-Au > OT-CdS.
Vertical Alignment of Single-Walled Carbon Nanotubes on Chemically Functionalized Silicon Substrates
Authors: Lee Ha-Jin , Park Hyeyoung , Koo Sunyoung , Lee Haiwon 
Published: April 2011

ABSTRACTCarbon nanotubes have been widely investigated as an essential component for fabricating nanoelectronic devices and for their numerous applications. We investigated the vertical alignment of single-walled carbon nanotubes (SWNTs) on chemically functionalized Si surfaces using chemical reactions between chemical groups in SWNTs and surfaces. For controlling the high selectivity of a specific chemical reaction, a pre-patterned 3-D nanostructure was used by using AFM anodization lithography for achieving the vertical alignment of SWNTs. To consider the subsequent chemical reaction with chemically modified Si surface, the carboxylic acid groups were converted into acid chloride groups followed by the reaction with chemically functionalized surfaces. The protruded structures on pre-patterned areas strongly suggest the vertically oriented SWNTs, and the distribution of the vertically aligned SWNTs becomes denser and their heights are longer with prolonged reaction time. The aspect ratio of SWNTs aligned on -OH functionalized surface is independent from the reaction time (H/W = 0.2). After random alignment of relatively shorter nanotubes on the substrate, their bundle size increases with increasing the reaction time due to strong van der Waals interaction between the lateral sides of nanotubes described as ‘nucleation growth’. Longer tubes get also adsorbed on the surface by increase in the bundle size and nanotube length, simultaneously. Based on the chemical reactions of the modified SWNTs with functionalized surfaces, selective attachments of SWNTs were carried out onto pre-patterned surfaces. Detailed characterization of aligned SWNTs will be discussed.
Optically Driven Micromanipulation Tools Fabricated by Two-photon Microstereolithography
Authors: Maruo Shoji , Ikuta Koji , Korogi Hayato 
Published: April 2011

ABSTRACTLight-driven micromanipulators have been developed by two-photon microstereolithography. The manipulators are driven and controlled by optical trapping. The torque of micromanipulator was successfully controlled on the order of femto-newton by adjusting the focal position of the trapped laser beam. Nanotweezers and a nanoneedle with probe tip of diameter 250 nm were fabricated and driven in a liquid. Such remote-controlled manipulation tools provide a unique and effective handling method of biological samples such as living cell, protein and DNA.
Control of indium surface segregation in GaAs layer on InGaP grown by MOVPE
Authors: Fukushima Y. , Nakano Y. , Shimogaki Y. 
Published: April 2011

ABSTRACTIn order to fabricate good hetero-interface of GaAs/InGaP system by metal-organic vapor phase epitaxy (MOVPE), we studied the indium atom distribution by X-ray photoelectron spectroscopy (XPS). The systematic XPS depth profile analyses of InGaP/GaAs revealed that InGaP surface contains an excess amount of indium atoms. The excess indium atoms diffuse into GaAs layer and cause surface segregation. We have developed a novel gas switching sequence to switch the growth from InGaP to GaAs. That is, after the growth of InGaP, trimethylgallium (TMGa) was pre-introduced to the reactor to terminate the excess amount of indium atoms on InGaP layer. Then tertiarybutylarsine (TBAs) was allowed to flow on the InGaP surface to initiate GaAs growth. This new sequence reduced the amount of indium atoms at the interface and contributed to suppress the inter-diffusion and surface segregation of indium atoms.
Lateral Epitaxial Overgrowth of InAs on (100) GaAs Substrates
Authors: Suryanarayanan Ganesan , Khandekar Anish A. , Hawkins Brian E. , Kuech Thomas F. , Babcock Susan E. 
Published: April 2011

ABSTRACTThe microstructure of epitaxial InAs thin films grown by MOCVD on mask-patterned “LEO” (lateral epitaxial overgrowth) GaAs and on unpatterned GaAs substrates was studied using double-crystal x-ray diffraction, scanning electron microscopy and cross-sectional transmission electron microscopy. This paper describes the improvement in crystal quality (factor of 20 reduction in x-ray rocking curve width), the order of magnitude reduction in dislocation density, and the rearrangement of the remaining extended defects that were observed in the LEO material when compared to the film grown on the unpatterned wafer.
Preparation of Optoelectronic Devices Based on AlN/AlGaN Superlattices
Authors: Holtz M. , Kipshidze G. , Chandolu A. , Yun J. , Borisov B. , Kuryatkov V. , Zhu K. , Chu S. N. G. , Nikishin S. A. , Temkin H. 
Published: April 2011

ABSTRACTWe present results on growth and fabrication experiments of AlN/AlGaN superlattices for ultraviolet (UV) optoelectronic devices. Superlattices with extremely short periods have been studied. The AlN “barrier” layers are 0.5 nm thick, and the AlxGa1-xN “wells” are 1.25 nm thick, with x ∼ 0.08. This combination gives an average AlN mole fraction of 0.63 across one full period. The superlattice periods, AlN mole fractions, and energy gaps are determined using TEM, X-ray diffraction, and optical reflectance. They are all consistent with each other. For device fabrication, p-i-n structures are grown doped with Si (n-type) and Mg (p-type). The acceptor activation energy of ∼ 0.2 eV is found. Mesa structures are plasma etched using chlorine chemistry. Etch rates of AlN are ∼ 1/3 those of GaN under identical circumstances. Etch rates of 250 nm/min are used for the device structures. A light emitting diode, with primary emission at 280 nm is reported, and a detector with sensitivity edge at 260 nm are reported.
Electrical isolation of p-type GaAsN epitaxial layers by ion irradiation
Authors: Gao Q. , Muller J. , Deenapanray P. N. K. , Tan H. H. , Jagadish C. 
Published: April 2011

ABSTRACTThe evolution of sheet resistance (Rs) of p-type conductive GaAs(1-x)Nx epilayers (x = 0.6%, 1.4%, and 2.3%) exposed to MeV 1H+, 7Li+, 12C+, and 16O+ ions and the stability of the formed electrical isolation during post-irradiation annealing were investigated. Results show that the threshold dose (Dth) to convert a conductive layer to highly resistive one close-to-linearly depends on original free carrier concentration and inversely depends on the number of irradiation-generated atomic displacements, and is independent of the nitrogen content in GaAsN layers. Increasing beam flux of 12C+ results in a lower Dth, whereas 1H+ beam flux does not affect it, showing the influence of collision cascade density. Results also show that irrespectively of the ion mass, the stability of electrical isolation formed in GaAsN is dependent on the ratio of the concentration of irradiation-created carrier traps to Dth. The electrical isolation can be preserved up to 550°C when the accumulated dose (D) is greater than 3.3 Dth.
Extremely Large Er Excitation Cross Section in Er,O-Codoped GaAs Light Emitting Diodes Grown by Organometallic Vapor Phase Epitaxy
Authors: Fujiwara Yasufumi , Koizumi Atsushi , Inoue Kentaro , Urakami Akira , Yoshikane Taketoshi , Takeda Yoshikazu 
Published: April 2011

ABSTRACTRoom-temperature Er-related electroluminescence (EL) properties have been investigated in Er,O-codoped GaAs (GaAs:Er,O) light emitting diodes (LEDs) grown by organometallic vapor phase epitaxy (OMVPE). Under forward bias, characteristic emission due to a luminescence center consisting of Er coordinated by O and As was clearly observed at room temperature, while the Er-related EL was undetectable under reverse bias. At lower current densities, the EL intensity increased linearly with the current density. Subsequently, the intensity exhibited a tendency to saturate at higher current densities. By analyzing the behavior with a fitting according to rate equations, the excitation cross section of Er ions due to current injection was determined to be approximately 10-15 cm2, which is by five orders in magnitude larger than that for optical excitation in Er-doped fiber amplifiers (10-20∼10-21 cm2).
Quantum Efficiency Modeling of Amorphous/Crystalline Silicon Heterojunction Photovoltaic Devices
Authors: Khalvati F. , Sivoththaman S. 
Published: April 2011

ABSTRACTAmorphous/crystalline silicon (a-Si/c-Si) heterojunctions are of particular importance in photovoltaic (PV) energy conversion in a cost-effective way. This is principally due to the low temperature (low-T) nature of the process. In this work, we have analyzed a (n)a-Si/(i)a-Si/(p)c-Si heterojunction solar cell structure using theoretical models for internal quantum yield (IQY) and I-V behavior. We considered low-quality (low bulk lifetime), cheaper substrates. Thin, low bulk lifetime substrates in combination with a low-T bulk passivation scheme and low rear surface recombination can lead to a cost effective device fabrication process with competitive conversion efficiency.
Photosensitive Amorphous Si Thin Films Prepared by Magnetron Technology.
Authors: Khlyap Galina , Brytan Victor 
Published: April 2011

ABSTRACTElectric field – induced effects are studied in thin films of amorphous Si grown by magnetron sputtering performed in continuous and pulse modes. Current-voltage characteristics are measured under the room temperature in different spectral ranges. It is shown that the investigated dependencies are of exponential character in all range of applied bias. Good photosensitivity was revealed by the samples prepared in continuous mode in the near-IR and visible interval. The samples grown by the pulse magnetron technology were shown room-temperature photosensitivity in near-IR range after 2000C hydrogenation.
Raman and magneto transport studies of MBE grown β-FeSi2, β-(Fe1-xCrx)Si2, and β-(Fe1-xCox)Si2
Authors: Srujana A. , Wadhawan A. , Srikala K. , Gorman B.P. , Cottier R.J. , Zhao Wei , Littler C.L. , Perez J.M. , Golding T.D. , Birdwell A.G. , Henrion W. , Rebien M. , Stauss P. , Glosser R. 
Published: April 2011

ABSTRACTIron disilicide shows great promise as a silicon based light emitter operating in the 1.3 to 1.5 μm wavelength range. However, there exists a number of questions related to the band structure and the ability to alloy and controllably dope the material both n and p type. In this paper we present Raman and magneto transport studies on β-FeSi2, β-(Fe1-xCrx)Si2, and β-(Fe1-xCox)Si2 grown by MBE. By comparing the spectra obtained for undoped and doped samples we provide a general overview of the effects of doping on the crystallinity of the material. The temperature dependent (4K<T<300K) magneto transport illustrates that Cr is a p-type dopant and Co is an n-type dopant in β-FeSi2.The temperature dependence of the resistivity indicates that the transport properties at higher temperatures are determined by free carriers whereas at lower temperatures impurity band conduction prevails.