bluuebunny/crossref_metadata_2025_split huggingface dataset:
Permittivity in Molecular Nanofilms
Authors: Vucenovic Sinisa , Ilic Dusan , Setrajcic Jovan , Sajfert Vjekoslav , Mirjanic Dragoljub 
Published: April 2011

AbstractA microscopic theory of dielectrical properties of thin molecular films, i.e. quasi 2D systems bounded by two surfaces parallel to XY planes was formulated. Harmonic exciton states were calculated using the method of two-time, retarded, temperature dependent Green's functions. It has been shown that two types of excitations can occur: bulk and surface exciton states. Analysis of the optical properties of these crystalline systems for low exciton concentration shows that the permittivity strongly depends on boundary parameters and the thickness of the film. Conditions for the appearance of localized exciton states have been especially analyzed.
Electron Energy Spectra of Single and Multiple AlGaN/GaN Quantum Dots with Spontaneous and Piezoelectric Polarization Effects
Authors: Praharaj Choudhury Jayant 
Published: April 2011

AbstractWe present numerical calculations of electron spectra of single and multiple coupled quantum dots based on Aluminium Gallium Nitride / Gallium Nitride heterostructures. The effect of spontaneous and piezoelectric polarization on the confinement potential seen by the electrons is taken into account through bound interface sheet charges. We also calculated the spectra without polarization effects for reference. For some quantum dot dimensions, the energy eigenvalues shift by several hundred meVs due to the polarization charges. We calculate the spectra for the two cases of box-shaped and cylindrical quantum dots. The latter case is an approximation to quantum dots with hexagonal-facet shapes recently reported in the literature. The quantum dots in our calculations are surrounded by vacuum in the lateral direction, but the same qualitative conclusions will hold if the dots are embedded in some material, as long as the barrier heights are large. For GaN vertical confinement of less than 30 angstroms, most of the bound states are associated with the lowest eigenvalue of the vertical confinement potential. This is also true for higher vertical confinement dimensions because the triangular potential seen by the electrons is the same for the lowest energy eigenstates. The electric field in the vertical direction is a strong function of the aluminium concentration in the AlGaN layer. As the AlGaN layer composition is varied from very high Al concentration to medium Al concentration, the spectra shift by several hundred meVs, referred to the onset of the continuous spectra. The transition frequencies between bound states and between bound and the lowest continuum states lie in the low to the high infra-red range, and can be varied over a wide range by both the dimensions and the barrier aluminium concentration. For the case of 4 coupled quantum dots formed by repeated AlGaN/GaN heterojunctions, we find that the polarization-induced electric fields lead to excessive band-bending and as a consequence there are fewer bound states compared to the spectrum calculated without polarization effects.
MOCVD Behaviors of Two-Sized InGaAs Ordered Nano-Bar Arrays Grown Selectively on a GaAs Substrate
Authors: Wang Benzhong , Chua Soo-Jin 
Published: April 2011

AbstractNanosphere lithography was used to form a nano-scaled SiO2 template on a GaAs substrate. Especially, a simple method for fabricating nanopatterns with multi feature sizes within one step has been invented. These nanopatterns, as a template, can be used to grow selectively ordered nanostructures arrays such as quantum dots, quantum bars with different feature sizes in one step. Two sized In0.25Ga0.75As nano-bar arrays have been successfully grown on a GaAs substrate by MOCVD.
Growth and Characterization of InAs Quantum Dot Enhanced Photovoltaic Devices
Authors: Hubbard Seth Martin , Raffaelle Ryne , Robinson Ross , Bailey Christopher , Wilt David , Wolford David , Maurer William , Bailey Sheila 
Published: April 2011

AbstractThe growth of InAs quantum dots (QDs) by organometallic vapor phase epitaxy (OMVPE) for use in GaAs based photovoltaics devices was investigated. Growth of InAs quantum dots was optimized according to their morphology and photoluminescence using growth temperature and V/III ratio. The optimized InAs QDs had sizes near 7×40 nm with a dot density of 5(±0.5)×1010 cm-2. These optimized QDs were incorporated into GaAs based p-i-n solar cell structures. Cells with single and multiple (5x) layers of QDs were embedded in the i-region of the GaAs p-i-n cell structure. An array of 1 cm2 solar cells was fabricated on these wafers, IV curves collected under 1 sun AM0 conditions, and the spectral response measured from 300-1100 nm. The quantum efficiency for each QD cell clearly shows sub-bandgap conversion, indicating a contribution due to the QDs. Unfortunately, the overarching result of the addition of quantum dots to the baseline p-i-n GaAs cells was a decrease in efficiency. However, the addition of thin GaP strain compensating layers between the QD layers, was found to reduce this efficiency degradation and significantly enhance the subgap conversion in comparison to the un-compensated quantum dot cells.
Surfactant-SWNT Assembly and Static Dielectrics of SWNTs
Authors: Wang Dan , Lu Wei , Zhang Ru , Li Zi-Chen , Chen Liwei 
Published: April 2011

AbstractIn this invited presentation, we report (1) the assembly of polymer surfactants at the single-walled carbon nanotube (SWNT) and water interface, which not only results in the dispersion of SWNTs in aqueous environments but also provides opportunities for controlled assembly of ternary complexes and the introduction of external stimuli-responsive SWNT dispersions; (2) the first experimental measurement of dc polarization of individual carbon nanotubes using modified scanning force microscopy techniques. The transverse dielectric constant of carbon nanotube is about 10, and this method could be used to distinguish metallic from semiconducting nanotubes.
Synthesis of Controllably Grown Carbon Nanotubes Interconnects
Authors: Lee Seon Woo , Katz David , Kornblit Avi , Lopez Daniel , Grebel Haim 
Published: April 2011

AbstractIntra-connects (bridges spanning across in plane electrodes), which were made of carbon nanotube (CNT), were fabricated by CO Plasma Enhanced Chemical Vapor Deposition (PECVD), ethanol CVD and pyrolitic CO CVD. CO PECVD has been used with CO/H2 mixture at relatively low temperatures. Its yield was relatively low though and the quality of CNT intra-connect was not to par. Ethanol CVD resulted in many more multi-wall carbon nanotube (MWCNT) than single-wall carbon nanotube (SWCNT) intra-connects. CO CVD was the most effective and simplest way to grow CNT interconnects among the three methods, yielding well-aligned and straight SWCNT bridges.
Application of the G'/D Raman Ratio for Purity Assessment of Multi-Walled Carbon Nanotubes
Authors: DiLeo Roberta , Landi Brian , Raffaelle Ryne 
Published: April 2011

AbstractCarbonaceous purity assessment methods are being sought after for all types of carbon nanotubes as a means to standardize the material metrology. Our most recent work has evaluated chemical vapor synthesized multi-walled carbon nanotubes (MWNTs). This effort included a protocol for assessment involving qualitative information from scanning electron microscopy (SEM) images and quantitative information from thermogravimetric analysis (TGA) and Raman spectroscopy. Presently, the analysis using Raman spectroscopy on a constructed sample set has been extended to a second excitation energy (HeNe laser at 1.96 eV) and the similar trends in the relative Raman peak ratios have been measured. In contrast to the G-band, the D and G' peaks demonstrate a Raman shift that is excitation energy-dependent, consistent with the double resonance theory. However, the Raman ratio of IG'/ID is independent of excitation energy and is observed to be the most sensitive to MWNT carbonaceous purity. Application of this approach to MWNT arrays grown on SiO2 is compared to conventional bulk powders synthesized under similar conditions. The MWNT arrays show a high degree of vertical alignment based upon SEM and a measured carbonaceous purity using the IG'/ID ratio of 75% w/w.
Doping of Al-catalyzed Vapor-liquid-solid Grown Si Nnanowires
Authors: Whang Sung Jin , Lee Sung Joo , Yang Wei Feng , Zhu Hai Chen , Gu Han Lu , Cho Byung Jin , Liew Yun Fook 
Published: April 2011

AbstractWe successfully synthesized high quality single crystal Si nanowires using Al catalyst via vapor-liquid-solid (VLS) mechanism, having diameters ranging from 10 to 200 nm with 10∽20 §­ of length. Characterization of physical and chemical properties of Al-catalyzed Si nanowires using transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) analysis showed that single crystal Si nanowires can be grown with Al-catalyst at 540 ¡C and selective etching of Al existing at the tip of nanowire can provide metal-free Si nanowires that are compatible with conventional Si-based IC process. By using plasma doping method, it was confirmed that the doping level can be controlled and the boron was successfully introduced on Si substrate with 3×1022/cm3 of peak doping concentration.
1-D and 2-D forms of Copper Sulfide: Electrochemical Deposition and Morphological Analysis
Authors: Singh Krishna Veer , Martinez-Morales Alfredo A. , Ozkan Mihrimah 
Published: April 2011

AbstractCopper sulfide is a material with immense potential for applications in photovoltaics. Particularly, copper sulfide 1-D nanostructures (i.e. nanowires, nanorods) with well-defined morphologies may enable new types of applications or may enhance the performance of existing photoelectric devices with quantum confinement effects. In this work, we report the synthesis of copper sulfide nanorods by simple, yet very effective template assisted electrochemical deposition. Before synthesizing 1-D copper sulfide nanorods, a detailed study was conducted on electrodeposited 2-D copper sulfide films to ascertain the right parameters for electrodeposition including; electrolyte composition, temperature, deposition potential and membrane type. Excellent structural properties of these resultant nanorods make them desirable for applications in the future nano-opto-electronic devices.
Scaffolding Carbon Nanotubes into Single-Molecule Circuitry
Authors: Collins Philip G. , Coroneus John G. , Weiss Gregory A. , Collins Philip G. 
Published: April 2011

AbstractWhile nanowires and nanotubes have been shown to be electrically sensitive to various chemicals, not enough is known about the underlying mechanisms to control or tailor this sensitivity. By limiting the chemically sensitive region of a nanostructure to a single binding site, single molecule precision can be obtained in order to study the chemoresistive response. We have developed techniques using single-walled-carbon-nanotube (SWCNT) circuits that enable single-site experimentation and illuminate the dynamics of chemical interactions. Discrete changes in the circuit conductance reveal chemical processes happening in real-time and allow SWCNT sidewalls to be deterministically broken, reformed, and conjugated to target species.
Development of Polymeric Micro/Nanostructures For Gene Delivery
Authors: Alyounes Dania , Yengo Christopher , Doran Tim , Lu Qi , Gonsalves Kenneth 
Published: April 2011

AbstractPluronic® polymers were screened for binding affinity to oligoribonucleotides (ORN) using fluorescence techniques. F127 (Mw 12600 g/mole) proved to have the strongest binding affinity. Urethane linkages were introduced into F127 and two other Pluronics, F38 (Mw 4700 g/mole) and F77 (Mw 6600 g/mole) to prepare polymers that were multiples of their respective initial molecular weights. A series of these polyurethane Pluronics were screened for binding affinity. Fluorescence studies showed a relationship between the molecular weight of the PO units and the binding affinity in the structures of the newly synthesized polyPluronics, especially in the case of F77. Light scattering confirmed the binding affinity between the ORN and F77 polymers. Particle size analysis showed an exponential increase until the critical micelle concentration. Other analogs of these polymers also studied for their binding affinity were poly(ester amines) and PINC.
Cell Response and Tissue Scaffold Triggers Investigated by Scanning Probe Recognition Microscopy
Authors: Chen Qian , Fan Y. , Kumar S. , Baczewski A. D. , Udpa L. , Ayres V. M. , Ahmed I. , Meiners S. , Rice A. F. 
Published: April 2011

AbstractTissue scaffolds have recently demonstrated widespread application in injury healing due to their biomimetic properties and their structural resemblance to the extracellular matrix in cell re-growth. The investigation of cell response to biomimetic triggers provided by tissue scaffolds will greatly extend the impact of this field.In this paper, the response of 3T3 NIH fibroblasts to 2D planar surfaces versus their response to nanofiber mat surfaces, which have 3D effects, are investigated. A difference in cell shape from triangular cell body with prominent vertices to triangular cell body with blunted vertices and increased cell-cell adhesions at such vertices was observed using fluorescent microscopy, optical microscopy and atomic force microscopy. A new and powerful atomic force microscopy technique developed by our group, Scanning Probe Recognition Microscopy, is introduced and implemented to directly recognize and auto-focus on fibroblast vertex regions.
Cluster Ion Beam Process for Nanofabrication
Authors: Yamada Isao , Toyoda Noriaki 
Published: April 2011

AbstractThis paper reviews gas cluster ion beam (GCIB) technology, including the generation of cluster beams, fundamental characteristics of cluster ion to solid surface interactions, emerging industrial applications, and identification of some of the significant events which occurred as the technology has evolved into what it is today. More than 20 years have passed since the author (I.Y) first began to explore feasibility of processing by gas cluster ion beams at the Ion Beam Engineering Experimental Laboratory of Kyoto University. Processes employing ions of gaseous material clusters comprised of a few hundred to many thousand atoms are now being developed into a new field of ion beam technology. Cluster-surface collisions produce important non-linear effects which are being applied to shallow junction formation, to etching and smoothing of semiconductors, metals, and dielectrics, to assisted formation of thin films with nano-scale accuracy, and to other surface modification applications.
Ion-Beam Assist Nano-Texturing of Films
Authors: Matias Vladimir , Sheehan Chris , Findikoglu Alp T. 
Published: April 2011

AbstractWe present an ion-beam based fabrication method for growth of single-crystal-like films that does not utilize epitaxy on single crystal substrates. We use ion-beam assisted texturing to obtain biaxial crystalline alignment in a film. This ion-beam assisted deposition (IBAD) texturing can be done on arbitrary, but smooth substrates, including flexible polycrystalline metal tapes. With IBAD texturing of MgO and subsequent homoepitaxial growth we have demonstrated an in-plane mosaic spread FWHM as low as 2° and out-of-plane alignment of 1°. The deposition system we use includes reel-to-reel tape transport for a linear transport of substrate materials through the deposition zones. This allows for high-throughput experimentation via a linear combinatorial experimental design.
Resolution Performance of Programmable Proximity Aperture MeV Ion Beam Lithography System
Authors: Gorelick Sergey , Sajavaara Timo , Laitinen Mikko , Puttaraksa Nitipon , Whitlow Harry J. 
Published: April 2011

AbstractAn ion beam lithography system for light and heavy ions has been developed at the University of Jyväskylä's Accelerator Laboratory. The system employs a programmable proximity aperture to define the beam. The proximity aperture is made up of four Ta blades with precise straight edges that cut the beam in the horizontal and vertical directions. The blade positions and dimensions are controlled by a pair of high-precision linear-motion positioners. The sample is mounted on a X-Y-Z stage capable of moving with 100 nm precision steps under computer control. The resolution performance of the system is primarily governed by the proximity aperture. Pattern edge sharpness is set by the beam divergence, aperture blade straightness, and secondary and scattered particles from the aperture blade edges. Ray tracing simulations using the object oriented toolkit GEANT4 were performed to investigate the beam spatial resolution on the sample defined by the proximity aperture. The results indicate that the edge-scattering does not significantly affect the pattern edge sharpness.
Modification of Surface Morphology of UHMWPE for Biomedical Implants
Authors: Oztarhan Ahmet , Sokullu Urkac Emel , Kaya Nusret , Yenigul Mesut , Tihminlioglu Funda , Ezdesir Ayhan , Zimmerman Robert , Budak Satilmis , Muntele C , Chhay Bopha , Ila Daryush , Oks Efim , Nikolaev Alexey , Tek Zekai , Eltem Rengin 
Published: April 2011

AbstractUHMWPE samples were implanted with metal and metal-gas hybrid ions (Ag, Ag+N, C+H, C+H+Ar, Ti+O ) by using improved MEVVA Ion implantation technique [1,2]. with an extraction voltage of 30 kV and fluence of 1017 ions/cm2 in an attempt to change their surface morphologies in order to understand the effect of ion implantation on the surface properties of UHMWPEs. Characterizations of the implanted samples with RBS , ATR - FTIR, spectra were compared with the un-implanted ones. Implanted and unimplanted samples were also thermally characterized by TGA and DSC. It was generally observed that C-H bond concentration seemed to be decreasing with ion implantation and the results indicated that the chain structure of UHMWPE were changed and crosslink density and polymer crystallinity were increased compared to unimplanted ones resulting in increased hardness. It was also observed that nano size cracks (approx.10nm) were significantly disappeared after Ag implantation, which also has an improved antibacterial effect. Contact angle measurements showed that wettability of samples increased with ion implantation. Results showed that metal and metal+gas hybrid ion implantation could be an effective way to improve the surface properties of UHMWPE to be used in hip and knee prosthesis.
Core-Satellite Metallic Nanoclusters in Silica Obtained by Multiple Ion Beam Processing
Authors: Mattei Giovanni , Bello Valentina , Mazzoldi Paolo , Pellegrini Giovanni , Maurizio Chiara , Battaglin Giancarlo 
Published: April 2011

AbstractIon irradiation has been used to transform spherical bimetallic AuAg nanocluster embedded in silica in a more complex structure made of a central cluster surrounded by a halo of smaller satellite nanoclusters, whose composition, size and distance from the central cluster can be tailored by controlling the irradiation parameters. This peculiar topology produces a red-shift of the surface plasma resonance of the composite through the electromagnetic coupling between the central cluster and the satellites. A calculation of the local field properties of the investigated systems within the fully-interacting generalized Mie theory showed that the satellite topology produces large local field enhancements around the central cluster.
Irradiation Effects of Methanol Cluster Ion Beams on Solid Surfaces
Authors: Takaoka Gikan , Kawashita Masakazu , Okada Takeshi 
Published: April 2011

AbstractIn order to investigate the interactions of methanol cluster ion beams with solid surfaces, Si substrates and SiO2 films were irradiated at different acceleration voltages. The sputtered depth increased with increase of the acceleration voltage. When the acceleration voltage was 9 kV, the sputtered depths of Si and SiO2 at a dose of 1×1016ions/cm2 were 1497.1 nm and 147.8 nm, respectively. The selectivity between Si and SiO2 surfaces arose from the volatility of the reaction products. Furthermore, the sputtering yield for the Si surface was approximately seven hundreds times larger than that by Ar monomer ion beams. This suggested that chemical sputtering was predominant for the methanol cluster ion irradiation. In addition, the etching and cleaning process by the methanol cluster ion irradiation was performed on the Si surfaces contaminated with a small amount of metal particles such as Au and Al. Thus, methanol cluster ion beams have unique characteristics such as surface etching and cleaning with high sputtering yield and smooth surface.
In Vitro Apatite Formation on Polymer Substrates Irradiated by the Simultaneous Use of Oxygen Cluster and Monomer Ion Beams
Authors: Kawashita Masakazu , Araki Rei , Takaoka Gikan H 
Published: April 2011

AbstractPolyethylene (PE) and silicone rubber substrates were irradiated at an acceleration voltage of 7kV and a dose of 1×1015 ions/cm2 by the simultaneous use of oxygen cluster and monomer ion beams, and then soaked in CaCl2 solution. Apatite-forming ability of the substrates was examined using a metastable calcium phosphate solution that had 1.5 times the ion concentrations of a normal simulated body fluid (1.5SBF). After the irradiation, the hydrophilic functional groups such as COOH and silicon oxide cluster (SiOx) were formed at the PE and silicone rubber surfaces, respectively. The hydrophilicity of the substrates was remarkably improved by the irradiation. The irradiated PE and silicone rubber substrates formed apatite in 1.5SBF, whereas unirradiated ones did not form it. These results suggest that the functional groups such as COOH groups and Si-OH groups induced apatite nucleation in 1.5SBF.
High Resolution XRD Studies of Ion Beam Irradiated InGaAs/InP Multi Quantum Wells
Authors: Dhamodaran S. , Sathish N , Pathak Anand P , Turos Andrzej , Avasthi Devesh K , Arora Brij M 
Published: April 2011

AbstractMulti quantum wells of InGaAs/InP grown by metal organic chemical vapor deposition have been irradiated using swift heavy ions. Irradiation has been performed using 150MeV Ag and 200MeV Au ions. Both as-grown and irradiated samples were subjected to rapid thermal annealing at 500 and 7000C for 60s. As-grown, irradiated and annealed samples were subjected to high resolution x-ray diffraction studies. Both symmetric and asymmetric scans were analyzed. The as-grown and Ag ion irradiated samples show sharp and highly ordered satellite peaks whereas, the Au ion irradiated samples show broad and low intense peaks. The higher order satellite peaks of the annealed samples vanished with increase of annealing temperature from 500 to 7000C, indicating mixing induced interfacial disorder. Annealing of irradiated samples show higher mixing and disorder and no higher order satellite peaks were observed. Negligible strain was observed after high temperature annealing of as grown samples. Strain values calculated from the X-ray studies indicate that the irradiated samples have higher strain which has been reduced upon annealing. This indicates that the annealing induced mixing occurs maintaining the lattice parameter close to that of the substrate. The effect of electronic energy loss for interface mixing has been discussed in detail. The role of incident ion fluence in combination with the electronic energy loss will also be discussed in detail. The results have been compared with the literature and discussed in detail.