bluuebunny/crossref_metadata_2025_split huggingface dataset:
Highly sensitive spin‐valve devices for chip‐cytometers
Authors: Roh Jong Wook , Son Oh‐Taek , Lee Young Tack , Lee Kyoung‐il , Jung Hyo‐Il , Lee Wooyoung 
Published: April 2009

AbstractThe highly sensitive spin‐valve devices integrated with a microfluidic channel have been studied for cell counting in a chip‐cytometer. The presence or absence of a single magnetic bead was successfully detected by direct measurement of fringe fields emanating from magnetic beads using spin‐valve devices. The real‐time detection was also successfully confirmed by the direct measurement of magnetic fields generated from the magnetic beads passing an active sensing area of a spin‐valve device integrated with a microfluidic channel. Our results show the possibility of implementing a chip‐cytometer for biological applications using the highly sensitive spin‐valve devices integrated with a microfluidic device. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic structure of hydrogenated amorphous Si1–xNx thin films using soft X‐ray emission and absorption measurements
Authors: Boyko Teak , Kasap Safa , Johanson Robert , Kobayashi S. , Aoki T. , Moewes Alexander 
Published: April 2009

AbstractHydrogenated amorphous silicon nitride thin films (a‐Si1–x Nx:H) with x = 0.46, 0.54, 0.55 and 0.58 have been studied. The optical bandgaps of these materials were 2.41, 2.78, 3.29 and 3.85 eV and Urbach edge bandgaps were 2.80, 3.27, 3.85 and 4.04 eV (W. C. Tan et al., J. Mater. Sci., Mater. Electron. 20, S15–S18 (2009) [1]), respectively. The bandgaps determined in this work using soft X‐ray spectroscopy (SXS) are 3.92, 4.43, 5.18 and 5.36 ± 0.25 eV. These large bandgaps are most likely due to the surface sensitivity of the SXS measurements and possible oxidation of the films. The conduction and valence band edges are determined using a linear regression fit and the bandgaps show a similar trend to that of the optical bandgap. Using Density Functional Theory (DFT) calculations for the two crystalline phases of silicon nitride the core hole interaction is accounted for in these bandgap determinations. This shows that both N and Si states are involved in bandgap transitions. Comparison of amorphous SXS spectra with that of crystalline phases shows that the Si bonding environment is similar to that of the beta phase while the N bonding environment is similar to that of the gamma phase. This shows there is a degree of short range order in the films similar to that of α,β‐Si3N4 indicating tetrahedral SiN4. The spectra also show that the Si states with 3s‐symmetry decrease as a function of nitrogen concentration which is evidence of Si–Si bonds that would increase the Si 3s states. This increase in Si 3s‐states effectively decreases the bandgap. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electroluminescence in plasma ion implanted silicon
Authors: Desautels Phillip R. , Bradley Michael P. , Steenkamp J. T. , Mantyka James 
Published: April 2009

AbstractElectroluminescent silicon is very desirable for its potential applications in computing and telecommunications. Plasma Ion Implantation (PII) is a means to modify the surface and sub‐surface properties of silicon to produce luminescent centres. Silicon to be treated with PII is immersed in low‐temperature plasma and biased to a high, negative voltage; this accelerates ions into the sample and implants them beneath its surface. The material is subsequently annealed in a furnace and fitted with thin gold and aluminium contacts. Samples of crystalline silicon were implanted with H ions, C ions, and N ions and found to emit visible light when subjected to electric current. Nearly every sample emitted light at ∼460 nm and ∼630 nm; these luminescence bands are commonly observed in X‐ray excited optical luminescence studies of silicon nanostructures and have been attributed to silicon dioxide (SiO2) and the silicon‐SiO2 interface, respectively [1]. Other luminescent bands may be the product of nanostructures and defects created by the implantation process and subsequent annealing. This presentation will explore in detail the results of these experiments and the potential of PII for modifying the luminescent properties of elemental silicon. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Rabi oscillations and photocurrent in quantum‐dot tunnelling junctions
Authors: Fainberg Boris , Nitzan Abraham 
Published: April 2009

AbstractMotivated by the experiments by Zrenner et al. [Nature 418, 612 (2002)], we study the influence of relaxation processes on converting Rabi oscillations in a strongly biased single‐quantum‐dot photodiode into deterministic photocurrents. We show that the behavior of a quantum dot with different tunnel rates for electron and holes is qualitatively different from that with the equal tunnel rates: in the latter case the current shows attenuating oscillations with the Rabi frequency. In contrast, for different electrons and holes tunnelling rates, the frequency of these oscillations diminishes, and they disappear beyond a definite asymmetry threshold. We give an analytical solution of the problem and a numerical example showing a different behaviour of the transferred charge in the small attenuation limit for equal and different tunnel rates for electrons and holes. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical properties of thick metal nanohole arrays fabricated by electron‐beam and nanosphere lithography
Authors: Hajiaboli Ahmad Reza , Cui Bo , Kahrizi M. , Truong Vo‐Van 
Published: April 2009

AbstractOptically thick metallic nanohole structures were fabricated using two different methods – electron‐beam and nanosphere lithography. The nanosphere lithography technique was based on self‐assembling of polystyrene or silica nanospheres (0.560–1.25 μm in diameter) followed by the deposition of a silver film. The holes size and periodicity of the patterns as well as optical properties (transmission and reflection in the Visible–NIR) of the structures were investigated. The extraordinary optical transmission (EOT) was studied experimentally in both structures and it was found to be dependent on the geometrical parameters (holes shape, diameter and periodicity of structures). As the samples were made for long range order, the effect of the defects like missing holes, change of periodicity or variation of the holes shape, were also studied. The experimental results, especially the position of the SPR band in the different nanohole structures, were compared with those found by simulation carried out with 3D FDTD (finite difference time domain). (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Controlling the optical properties of nanostructured TiO2 thin films
Authors: Hawkeye Matthew M. , Brett Michael J. 
Published: April 2009

AbstractWe have studied the optical properties of nanostructured TiO2 films and demonstrated the ability to tune the refractive index of the material over a wide range. The nanostructured films are fabricated using glancing angle deposition, which provides the ability to precisely control the density of the deposited film. Film morphology was examined using scanning electron microscopy and the films were optically characterized by polarized‐reflectance measurements. A simple isotropic homogeneous model, which is shown to be a good approximation of the film, is used to determine the optical constants from the reflectance measurements. Improvements to the model are suggested. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Unconventional control of excited states of a dimer molecule by a localized light field between metal nanostructures
Authors: Iida Takuya , Ishihara Hajime 
Published: April 2009

AbstractWe have made a theoretical study of the spatial interplay between the localized light field (LLF) and the electronic wavefunction of molecules. When the LLF has a nanoscale spatial variation comparable to a molecular wavefunction, this interplay is crucial to determine the optical response of molecular excited states. Such a condition can be realized in case that a molecule is lying in the vicinity of a metal nanogap. By using the calculation method applicable to arbitrary‐shaped samples, we demonstrate a drastic enhancement of the response electromagnetic field from an optical forbidden state whose magnitude is comparable to that from an allowed state. The obtained result indicates that we have a possibility to control the excited states of molecules by designing the LLF with metal nanostructures. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Homoepitaxial growth of high‐quality nonpolar ZnO films by MOCVD and evaluation of the homoepitaxial ZnO films by XRD measurement for asymmetric planes
Authors: Kashiwaba Yasuhiro , Abe Takami , Nakagawa Akira , Endo Haruyuki , Niikura Ikuo , Kashiwaba Yasube 
Published: April 2009

AbstractCharacteristics of homoepitaxial high‐quality nonpolar ZnO (11$ \bar 2 $0) films and a useful measurement method for determining structures of those films are described. Homoepitaxial growth of high‐quality nonpolar ZnO (11$ \bar 2 $0) films could be achieved by atmospheric‐pressure metal organic chemical vapor deposition using zinc acetylacetonate and oxygen gas. The value of full width at half‐maximum (FWHM) of X‐ray rocking curves (XRCs) of asymmetrical ZnO (20$ \bar 2 $0) and (11$ \bar 2 $2) planes increased with increase in oxygen gas flow rate, and the change in FWHM value corresponded to FWHM of near‐band‐edge emission of photoluminescence spectra. On the other hand, the FWHM value of the XRC of the symmetrical ZnO (11$ \bar 2 $0) plane did not change with change in oxygen gas flow rate, and the FWHM values of all samples were nearly equal to the FWHM value of a single crystal ZnO (11$ \bar 2 $0) substrate. The smallest FWHM values of XRCs of ZnO (11$ \bar 2 $0), (20$ \bar 2 $0) and (11$ \bar 2 $2) planes in the sample grown under the condition of an oxygen gas flow rate of 50 sccm were about 30 arcsec, 35 arcsec and 40 arcsec, respectively. These results indicate that the homoepitaxial ZnO (11$ \bar 2 $0) film has good crystallinity. XRC measurement for asymmetrical planes is useful for evaluating homoepitaxial ZnO (11$ \bar 2 $0) films. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ensemble effect on Rabi oscillations of excitons in quantum dots
Authors: Kujiraoka Mamiko , Ishi‐Hayase Junko , Akahane Kouichi , Yamamoto Naokatsu , Ema Kazuhiro , Sasaki Masahide 
Published: April 2009

AbstractWe observed excitonic Rabi oscillations (ROs) in quantum dots (QDs) by four‐wave mixing (FWM) and pump‐probe techniques. When a large number of QDs are excited by a spatially nonuniform laser, the inhomogeneous distribution of the transition dipole moments of the QD excitons and the spatial distribution of the input electric field induce distribution of the Rabi frequencies. We investigated this ensemble effect on the ROs of the excitonic polarization and the excitonic population observed in the FWM and pump‐probe signals. By calculating the FWM and pump‐probe signals including the Gaussian distribution of the pulse area, we first showed that a part of the ensemble effect can be cancelled out only in case of the ROs of the excitonic polarization. This reflects the differences between the characteristics of excitonic polarization and population. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sensitization efficiencies in Er‐doped SiOx films containing amorphous or crystalline silicon nanoclusters
Authors: Lenz F. , DeCorby R. , Meldrum A. 
Published: April 2009

AbstractA suite of SiOx films with oxygen concentrations ranging from x = 1 to 1.8 (25 at% to 3.6 at% excess silicon) were synthesized by physical vapour deposition. Erbium was incorporated by co‐evaporation of erbium metal to a concentration of about 0.2 at%. A subsequent annealing step was performed at temperatures ranging from 400 °C to 1100 °C to induce phase separation and cluster growth, and to optically activate erbium ions. This range of compositions and annealing temperatures was used to generate a fluorescence map for nanocluster‐sensitized Er3+. Photoluminescence (PL) spectra were measured in the visible and near‐infrared wavelength regions to explore the nature of the energy transfer between Si‐NCs and Er3+ ions. The highest PL intensities for undoped films occurred for samples annealed above 1000 °C, containing silicon nanocrystals. In contrast, in Er‐doped films the strongest Er3+ emission at 1.54 μm was observed from films annealed at temperatures below 1000 °C, demonstrating that amorphous Si nanoclusters support effective energy transfer to the Er3+ ions. The sensitization was most efficient when the NC peak emission wavelength was near 660 nm (1.88 eV) matching the energy of the 4F9/2 band of Er3+ ions in a silica host. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Impact ionization in semiconductors: recent progress on non‐local effects
Authors: Marsland John S. 
Published: April 2009

AbstractA model of the ionization pathlength PDF is reformulated with new parameters that have more physical significance and allow further investigation. The transition from the dead space effect to the dead space plus resonance effect is investigated and a new measure, the overshoot factor, is suggested as the method for indicating the degree of resonant behaviour. The non‐local model is extended for non‐uniform electric field profiles. When this extended model is fitted to Monte Carlo data derived for four different electric field profiles, a fairly consistent set of parameters is found. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Luminescence simulations of ensembles of silicon nanocrystals
Authors: Lockwood Ross , Meldrum Al 
Published: April 2009

AbstractThe luminescence of silicon nanocrystals (NCs) has attracted a great deal of interest due to the numerous potential photonic applications of light‐emitting silicon. However, the excitation mechanisms and cluster–cluster interactions in densely‐packed ensembles, as well as the recombination processes that influence the emission spectrum and lifetime are not yet well understood. In order to generate a more complete picture of the controlling parameters in the luminescence, a dynamic Monte Carlo model that incorporates several key physical processes for luminescent nanocrystal ensembles is developed. The model simulates Forster‐type multipole energy transfer, tunnelling interactions, radiative decay and non‐radiative trapping in physically realistic (lognormal) distributions of silicon NCs. The results of the simulation illustrate the effects of the NC size distribution, homogeneous and inhomogeneous broadening, NC packing density, and non‐radiative trapping on the ensemble luminescence spectrum. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photonic properties and applications of glass micro‐ and nanospheres
Authors: Righini Giancarlo C. , Cosi Franco , Conti Gualtiero Nunzi , Pelli Stefano , Soria Silvia , Moser Enrico , Jestin Yoann , Ferrari Maurizio , Féron Patrice , Chiasera Alessandro , Chiappini Andrea , Armellini Cristina 
Published: April 2009

AbstractFabrication, morphological and spectroscopic assessment of micro‐ and nano‐spheres are reported. Spheres with size ranging from few hundreds of nm to few hundreds of μm have been prepared by different methods, i.e. sol–gel, melting and core‐shell techniques. Pure and rare‐earth‐doped spheres find their major applications as microsensors and microlasers, respectively. We refer here to Erbium‐activated systems only: (i) coated micro spheres where the silica core, obtained by telecom fiber melting, is coated with an Er3+–70SiO2–30HfO2 film; (ii) Er3+‐activated microspheres obtained from silicate‐modified glasses and phosphate glasses using a plasma torch; (iii) sol–gel Er3+‐doped silica micro‐ and nano‐spheres. The whispering gallery mode spectra were analysed as a function of sphere diameter, thickness of coating (if any) and Erbium content. Photoluminescence spectra of different systems gave interesting indications on the potential of some activated microspheres for lasing applications. For instance, sol–gel Er3+‐activated core‐shell‐like structures exhibited a lifetime of 12.8 ms, leading to a quantum efficiency (QE) of 71%. Even higher QE (∼76%) was estimated in sol–gel Er3+‐silica spheres. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
All‐photonic switching in nanophotonic quantum wells
Authors: Singh Mahi R. 
Published: April 2009

AbstractWe have studied the absorption phenomenon in photonic quantum wells doped with an ensemble of three‐level nanoparticles. Photons are confined in the quantum well due to the band structure engineering. The bound states of the confined photon are calculated by using the transfer matrix method and it is found that the number of bound states in the quantum well depends on the size and the depth of the quan tum well. A probe lasers is applied to monitor the absorption spectrum. Nanoparticles are interacting with the bound photons within the quantum well. It is found that when the resonance energy of nanoparticles lies near the ground bound state, the system becomes transparent. These properties can be used to make new types of optoelectronic devices. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dipole–dipole interaction in nanoscale photonic quantum wells
Authors: Singh Mahi R. 
Published: April 2009

AbstractThe dipole–dipole interaction (DDI) has been studied in photonic quantum wells are simulated from two photonic crystals say A and B. An ensemble of nanoparticles is doped within the quantum well layer. Nanoparticles are interacting with each other via DDI. The absorption spectrum has been calculated by using the time dependent Schrodinger equation method. A probe field is applied to measure the absorption spectrum. Numerical simulations for the absorption coefficient have been performed. It has been found that in the absence of DDI the spectrum has two peaks and a minimum at zero detuning. However, in the presence of the large DDI coupling both peaks disappear and a large minimum appears. This means that the positions and heights of peaks can be changed due to DDI interaction. This study can be used to make new types of optical devices. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Light emission from different ZnO junctions and nanostructures
Authors: Willander M. , Lozovik Yu. E. , Wadeasa A. , Nur O. , Semenov A. G. , Vonorova N. S. 
Published: April 2009

AbstractWe will discuss our experimental results for optical spectra produced by hole‐injection from different p‐type organic and inorganic materials into n‐type ZnO nanowires. The influence of different growth techniques and conditions on the nanowires and their emission spectral characteristics will then be analyzed and discussed. The latest findings on the mixture of the green emission band responsible for visible light emission from ZnO and the blue light emission from the organic polymer will be presented. Different high brightness light emitting diodes (HB‐LEDs) from our grown ZnO nanowires are demonstrated. The p‐type multi layer organic structures contain PEDOT:PSS as hole injectors combined with a hole transporting layer, and in some structures, a final top electron blocking/hole barrier stepping layer is placed. The purpose of this layer is to adjust the hole and electron emission from the corresponding junction side to optimize the LED performance. Structural scanning electron microscopy (SEM), electrical (I –V characteristics), photoluminescence (PL) and electroluminescence (EL) characteristics of these devices are displayed. Theoretically, we study the superfluidity of a two‐dimensional system of excitonic polaritons in an optical microcavity with an embedded quantum well. Using the effective low‐energy action for thermodynamic phase fluctuations, we obtain an expression for the analogue of the superfluid density in the system in terms of the “current–current” correlation function. The Kosterlits–Thouless transition temperature to the superfluid state as a function of the controlling parameters is calculated. Two methods are considered for producing traps for a polariton system in an optical microcavity. The behaviour of a two‐component Bose condensate of photons and excitons is analyzed theoretically for both types of the trap. The Bose condensate is described by the coupled system of equations of the Gross–Pitaevskii type. The approximate wave functions and the spatial profiles of coupled photon and exciton condensates are obtained. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Preface: Phys. Status Solidi B 246/5
Authors: Machura Łukasz , Dajka Jerzy , Zipper Elżbieta 
Published: April 2009

AbstractEvery second year the Department of Theoretical Physics at the University of Silesia, Katowice, Poland, organizes the International Conference on Theoretical Physics. The XXXII meeting “Coherence and Correlations in Nanosystems” took place in September 2008 in Ustroń, Poland. The conference focused on current and important topics related to coherence and correlations in small systems. Special emphasis was given to the areas of physics at the border between theoretical solid state physics and nanophysics. The broad spectrum of topics covered during the six days of the conference can be summarized into the following five points:1. Quantum information and computation,2. Transport phenomena in nanosystems,3. Superconductivity and magnetism at the nanometer scale,4. Inhomogeneous systems,5. Ultracold atoms in optical lattices.The careful selection of the topics allowed the organizers of the conference to bring together distinguished scientists from different areas of physics. This in turn resulted in an effective cooperation between specialists and gave an excellent opportunity to exchange ideas. Thanks to the speakers and participants the 2008 conference maintained its international character and highest scientific quality. Both invited and contributed presentations were followed by fruitful formal and informal discussions.We would like to express our gratitude to all authors and referees whose effort allowed us to prepare this excellent issue. We also thank the editorial staff of physica status solidi for their kind assistance (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of different sealing conditions on the seal strength of polypropylene films coated with a bio‐based thin layer
Authors: Farris Stefano , Cozzolino Carlo Alessio , Introzzi Laura , Piergiovanni Luciano 
Published: April 2009

AbstractThis paper presents the results of an investigation through the design of experiment technique regarding the influence of temperature, dwell time and bar pressure on the heat seal strength of oriented polypropylene films coated with a gelatin‐based thin layer. This chemometric approach allowed achieving a thorough understanding of the effect of each independent factor on the two different responses (maximum force and strain energy) considered in this work as a measure of the strength necessary to break the bond across the sealed interface. Surprisingly, the factor affecting both responses the most was the bar pressure rather than the sealing temperature. Moreover, whereas the bar pressure negatively affected the seal strength of coated polypropylene films, the sealing temperature had a positive effect. Dwell time did not have any significant influence as a main factor, while influencing negatively the seal strength as an interaction term (i.e. time × pressure), together with the further interaction temperature × pressure. The mathematical models obtained for the two responses provided different results in terms of fitting capability (R2) and prediction ability (Q2). In particular, for the maximum force response, R2 and Q2 were equal to 0.571 and 0.405, respectively, whereas the model supporting the strain energy response gave R2 = 0.932 and Q2 = 0.937, highlighting that for quantifying the seal strength, the energy necessary to break a seal is a better measure than the maximum force. The highest seal strength values obtained during this work were of 0.6615 N and 19.6 N·mm for maximum force and strain energy, respectively. Copyright © 2009 John Wiley & Sons, Ltd.