bluuebunny/crossref_metadata_2025 huggingface dataset:
Thinking differently about cultural diversity: Using postcolonial theory to (re)read science education
Authors: Carter Lyn
Published: October 2004

This paper makes use of postcolonial theory to think differently about aspects of cultural diversity within science education. It briefly reviews some of the increasing scholarship on cultural diversity, and then describes the genealogy and selected key themes of postcolonial theory. Postcolonial theory as oppositional or deconstructive reading practice is privileged, and its practical application illustrated by using some of these key ideas to (re)read Gloria Snively and John Corsiglia's (2001) article “Discovering indigenous science: implications for science education” and their rejoinder, from the special issue of Science Education (Vol. 85, pp. 6–34) on multiculturalism and science education. While many would regard the expressed views on diversity, inclusivity, multiculturalism, and sustainability to be just and equitable, postcolonial analysis of the texts reveals subtle and lingering referents that unwittingly work against the very attitudes Snively and Corsiglia (2001) seek to promote. Such postcolonial analyses open up thinking about the material and cultural conditions in which science education is produced, circulated, interpreted, and enacted. They also privilege a unique methodology already prominent in academic inquiry that is yet to be well explored within science education. Finally, I conclude this paper with some general comments regarding postcolonialism and the science education scholarship on cultural diversity. © 2004 Wiley Periodicals, Inc. Sci Ed 88:819–836, 2004
Deliberate learning in corporate acquisitions: post‐acquisition strategies and integration capability in U.S. bank mergers
Authors: Zollo Maurizio , Singh Harbir
Published: October 2004

This paper introduces a knowledge‐based view of corporate acquisitions and tests the post‐acquisition consequences on performance of integration decisions and capability‐building mechanisms. In our model, the acquiring firm decides both how much to integrate the acquired firm and the extent to which it replaces this firm's top management team. It can also learn to manage the post‐acquisition integration process by tacitly accumulating acquisition experience and explicitly codifying it in manuals, systems, and other acquisition‐specific tools. Using a sample of 228 acquisitions in the U.S. banking industry, we find that knowledge codification strongly and positively influences acquisition performance, while experience accumulation does not. Furthermore, increasing levels of post‐acquisition integration strengthen the positive effect of codification. Finally, the level of integration between the two merged firms significantly enhances performance, while replacing top managers in the acquired firm negatively impacts performance, all else being equal. Implications are drawn for both organizational learning theory and a knowledge‐based approach to corporate strategy research. Copyright © 2004 John Wiley & Sons, Ltd.
Transient Posttransplant Graft-versus-Host Lymphadenopathy
Authors: Nodit Laurentia , Murase Noriko , Reyes Jorge D. , Mazariegos George V. , Sindhi Rakesh , Jaffe Ronald
Published: October 2004

There is sparse information in humans on graft-versushost (GVH) lymphadenopathy. A 15-month-old male received a liver and small bowel transplant for short bowel after gastroschisis. At 21 days he developed a GVH-like skin rash. Flow cytometry demonstrated 16.1% circulating donor cells. Polymerase chain reaction for Epstein-Barr virus was negative. Two months later, the rash recurred with diffuse lymphadenopathy. Lymph node biopsy showed effaced architecture without visible follicles, large numbers of CD79a+ immunoblasts interspersed with smaller CD3+ and CD8+ cells, and prominent dendritic cell hyperplasia. Human herpes virus 8, cytomegalovirus, and EBER-1 probes were negative, as was polymerase chain reaction for human herpes virus 6. Allograft intestinal biopsies on days 10 and 24 had a similar infiltrate. The features appeared to be those of lymphocytes trafficking between the graft and host with a mixed lymphocyte reaction in situ, a GVH-type reaction without tissue damage. The reaction was self-limiting in the intestinal graft, and the lymphadenopathy resolved with some decrease in immunosupression. Circulating donor cells fell to 2.5% by day 62, and the child has been rejection free on low-dose immunosuppression.
Climate feedback from wetland methane emissions
Authors: Gedney N. , Cox P. M. , Huntingford C.
Published: October 2004

The potential for wetland emissions to feedback on climate change has been previously hypothesised [Houghton et al., 2001]. We assess this hypothesis using an interactive wetlands scheme radiatively coupled to an integrated climate change effects model. The scheme predicts wetland area and methane (CH4) emissions from soil temperature and water table depth, and is constrained by optimising its ability to reproduce the observed inter‐annual variability in atmospheric CH4. In transient climate change simulations the wetland response amplifies the total anthropogenic radiative forcing at 2100 by about 3.5–5%. The modelled increase in global CH4 flux from wetland is comparable to the projected increase in anthropogenic CH4 emissions over the 21st century under the IS92a scenario.
Propagation of electron and proton shock‐induced aurora and the role of the interplanetary magnetic field and solar wind
Authors: Meurant M. , Gérard J.‐C. , Blockx C. , Hubert B. , Coumans V.
Published: October 2004

Shock‐induced aurora observed with satellite‐borne ultraviolet imagers shows distinct characteristics from the more common and extensively studied aurora generated during magnetospheric substorms. It is initiated in the noon sector immediately following dynamic pressure pulses associated with the arrival of enhanced solar wind plasma at the front of the magnetosphere. The auroral brightening rapidly propagates toward the dawn and dusk sectors and may eventually trigger the development of an auroral substorm on the nightside. The FUV imaging system on board the IMAGE satellite has the ability to discriminate between proton and electron precipitation. This feature has been used to study the morphology and dynamics of the electron and proton precipitation following pulse‐induced magnetospheric perturbations. A different dynamic is observed for aurora caused by electron and proton precipitation, as well as the important role played by the north‐south component of the interplanetary magnetic field. The propagation from the noon to the night sector mainly occurs through the afternoon region for proton precipitation and the morning sector for electron aurora, as expected from azimuthal drift of newly injected plasma. The asymmetry of the precipitation distribution around the noon‐midnight axis is more pronounced during negative Bz periods, when activity is the most important. The magnitude of both the interplanetary magnetic field and the solar wind speed appears well correlated with the precipitated power, by contrast with the solar wind density and the magnitude of the dynamic pressure, which appear to play a minor role. It is suggested that adiabatic compression and plasma waves play an important role on the locations of electron and proton precipitation in the dayside.
Ba
0.5
Sr
0.5
TiO
3
–
Bi
1.5
Zn
1.0
Nb
1.5
O
7
composite thin films with promising microwave dielectric properties for microwave device applications
Authors: Yan L. , Kong L. B. , Chen L. F. , Chong K. B. , Tan C. Y. , Ong C. K.
Published: October 2004

Crack-free, dense, and uniform Ba0.5Sr0.5TiO3(BST)–Bi1.5Zn1.0Nb1.5O7(BZN) composite thin films were deposited on (100)LaAlO3, (100)SrTiO3, and (100)MgO substrates via a pulsed laser deposition, using a combined target of BST and BZN ceramics. Phase composition and microstructure of the BST-BZN thin films were characterized by x-ray diffraction and scanning electron microscopy. The films, on LAO, STO, and MgO substrates, showed zero-field microwave (∼7.7GHz) dielectric constants of 471, 435, and 401, dielectric loss tangents of 0.0048, 0.0043, and 0.0037, and dielectric tunabilities of 6.2%, 6.0%, and 5.7% at ∼8.1kV∕cm, respectively. The good physical and electrical properties of the BST–BZN composite thin films make them promising candidates for microwave device applications.
Reynolds-averaged turbulence model for magnetohydrodynamic dynamo in a rotating spherical shell
Authors: Hamba Fujihiro
Published: October 2004

Numerical simulation of the magnetic field in a rotating spherical shell was carried out to assess and improve the Reynolds-averaged turbulence model for magnetohydrodynamic flows. In the three-equation model the transport equations for the turbulent energy, its dissipation rate, and the turbulent helicity are solved in addition to the mean magnetic field. The turbulent electromotive force involved in the magnetic field equation is expressed in terms of the α dynamo and turbulent diffusivity terms. Since the model was improved considering the realizability condition for the turbulent electromotive force, steady state solutions were obtained even in the case of rapidly rotating system such as the Earth. Profiles of the magnetic field, the turbulent energy, and the turbulent helicity as well as their transport equations were examined to check the dynamo mechanism expressed in the model. The dependence on the system rotation and on model constants was examined to assess the model performance.
Enhanced binding revisited for a spinless particle in nonrelativistic QED
Authors: Catto Isabelle , Exner Pavel , Hainzl Christian
Published: October 2004

We consider a spinless particle coupled to a quantized Bose field and show that such a system has a ground state for two classes of short-range potentials which are alone too weak to have a zero-energy resonance.
Photon tunneling via surface plasmon coupling
Authors: Passian A. , Wig A. , Lereu A. L. , Meriaudeau F. , Thundat T. , Ferrell T. L.
Published: October 2004

The measurement of a photonic signal via plasmon-plasmon coupling in curved thin metal films is presented. In domains of subwavelength dimension, we calculate the resonant dispersion relations by modeling the curved thin film as a single sheeted hyperboloid of revolution. We show that several such surface modes are accessible optically at frequencies below the plasma frequency of the metal.
Radially sheared azimuthal flows and turbulent transport in a cylindrical plasma
Authors: Tynan G. R. , Burin M. J. , Holland C. , Antar G. , Crocker N. , Diamond P. H.
Published: October 2004

A radially sheared azimuthal flow is observed in a cylindrical helicon plasma device without any apparent external sources of angular momentum input. Broadband fluctuations combined with a chain of coherent structures are observed, turbulent particle transport across the shear layer is inhibited, and energy appears to be transferred from linearly unstable intermediate wave numbers into both larger and smaller spatial scales that are linearly stable. The shape of the radial plasma potential profile associated with the azimuthal flow is in agreement with published theory, and the flow magnitude is consistent with estimates of the turbulent Reynolds stress.
Effect of metastable atoms on near-wall voltage drop in the afterglow of a noble-gas radio-frequency inductive coupled plasma
Authors: Demidov V. I. , DeJoseph C. A. , Kudryavtsev A. A.
Published: October 2004

It is shown that the creation of fast electrons by reactions involving metastable atoms may dramatically increase the near-wall potential drop in the afterglow of an rf-driven plasma. This results in a corresponding increase in the energy of ions incident on the walls of the discharge. This effect may be important in applications such as rf plasma processing.
On the Bose condensation in some model of a nonideal Bose gas
Authors: Sankovich D. P.
Published: October 2004

A model of a nonideal Bose gas with a repulsive interaction is considered. It is proved that there is not macroscopic occupation of the ground state in the thermodynamic limit in this model, but nevertheless the generalized condensation occurs.
Solution of the dual reflection equation for An−1(1) solid-on-solid model
Authors: Yang W.-L. , Sasaki R.
Published: October 2004

We obtain a diagonal solution of the dual reflection equation for the elliptic An−1(1) solid-on-solid model. The isomorphism between the solutions of the reflection equation and its dual is studied.
Analytic solution for entangled two-qubit in a cavity field
Authors: Abdel-Aty Mahmoud , Obada Abdel-Shafy F.
Published: October 2004

An exact solution of the time-dependent master equation that describes the evolution of two two-level qubits (ions or atoms) within a perfect cavity for the case of multiphoton transition and in the presence of both the Stark shift and phase shift is obtained. Employing this solution, the significant features of the entanglement when a second qubit is allowed to interact with cavity mode and becomes entangled with the first qubit are investigated in the context of the measure defined by negative eigenvalues for the partial transposition of the density operator. The effects of Stark shift, distance between the two qubits, and an instantaneous phase shift experienced by the second qubit on the entanglement and probability amplitudes are indicated. It has been shown that the entanglement as well as the intensity are markedly affected by different parameters when the nonlinear two-photon process is involved. Moreover, the quasiprobability distribution function is investigated before and after the sudden phase shift experienced by the second qubit. We believe that this may throw some light on the question of the entanglement of multi-qubit systems.
Organic field-effect transistors with electroplated platinum contacts
Authors: Majewski L. A. , Schroeder R. , Grell M.
Published: October 2004

Recent developments in organic transistor semiconductors and engineering have led to a situation where the performance of state-of-the-art organic transistors (organic field-effect transistors) often is limited by the resistance at the metal/semiconductor contacts, rather than the semiconductor channel. This letter shows that organic transistor contacts can be improved by the most important industrial process for the deposition of noble metals, electroplating. The advantages of electroplating over vacuum-based techniques such as evaporating and sputtering, in particular for the deposition of platinum (Pt), are discussed.
Nonlinear saturation of laser driven plasma beat wave by oscillating two-stream instability
Authors: Gupta D. N. , Singh K. P. , Sharma A. K. , Jaiman N. K.
Published: October 2004

Two copropagating lasers, having frequency difference Δω≈ωp, drive a plasma wave. The plasma beat wave amplitude increases with time initially due to the laser beams. As time grows, the plasma beat wave acquires large amplitude and it becomes susceptible to oscillating two-stream instability producing shorter wavelength Langmuir wave sidebands and a low frequency electrostatic mode. The decayed sidebands divert the energy of plasma beat wave by oscillating two-stream instability and saturate it.
Formation of macroscopic structures in partially ionized magnetoplasmas
Authors: Shukla P. K.
Published: October 2004

It is shown that the governing nonlinear equations for a partially ionized magnetoplasma admit large-scale (in comparison with the ion skin depth) structures on a scale size that is controlled by the neutral fluid mass density. Implications of our investigation to macroscopic magnetic field structures in the interstellar plasma are discussed.
Thermal degradation of electrical properties and morphology of bulk single-crystal ZnO surfaces
Authors: Khanna Rohit , Ip K. , Heo Y. W. , Norton D. P. , Pearton S. J. , Ren F.
Published: October 2004

Bulk ZnO substrates were rapid thermal annealed in either air or N2 at temperatures up to 500°C. The root-mean-square roughness of the surface as measured by atomic force microscopy begins to increase even after 200°C anneals in N2 or 300°C in air. The Schottky barrier height, ΦB, obtained from Pt∕Au diodes fabricated on these surfaces shows a decrease in effective barrier height upon annealing from 0.35eV in control samples to ∼0.30eV in those annealed at 400°C and an increase in the saturation current density (from 4Acm−2 in the control samples to 17–37Acm−2 in the annealed samples). These results show that the ZnO surface is degraded by quite low annealing temperatures and care must be exercised in designing the thermal budget for processing of ZnO devices. At much higher annealing temperatures (1000°C), the surface completely decomposes to leave metallic Zn droplets.
Hydrogen and deuterium incorporation and transport in hafnium-based dielectric films on silicon
Authors: Pezzi R. P. , Miotti L. , Bastos K. P. , Soares G. V. , Driemeier C. , Baumvol I. J. R. , Punchaipetch P. , Pant G. , Gnade B. E. , Wallace R. M. , Rotondaro A. , Visokay J. M. , Chambers J. J. , Colombo L.
Published: October 2004

Hydrogen and deuterium incorporation into nitrided and non-nitrided hafnium silicate films on Si during thermal annealing in H1- and H2-containing atmospheres was investigated. H1 profiling was accessed by means of nuclear resonant reaction profiling, whereas H2 incorporation was quantified by nuclear reaction analysis. The effects of preannealing in different atmospheres and temperatures were determined, as well as the losses of H1 and H2 from these structures during postannealing in vacuum. The results reveal a rather uniform depth distribution of incorporated H1, in striking contrast with previous studies on hydrogen in silicon oxide and oxynitrides and hafnium oxide films on Si. These results are discussed in terms of the defects present in each one of the structures studied here.
Global classical solution of the Vlasov–Maxwell–Landau system near Maxwellians
Authors: Yu Hongjun
Published: October 2004

We consider a classical model in the kinetic theory of plasma—the Vlasov–Maxwell–Landau system. Global in time classical solutions near Maxwellians are constructed for hard potential and soft potential, i.e., γ⩾−1. The construction of global solution is based on an energy method. Meanwhile, global classical solutions of the Vlasov–Poisson–Landau system near Maxwellians for γ⩾−1 and the exponential decay of such solutions are obtained.
Bond length contraction in Au nanocrystals formed by ion implantation into thin SiO2
Authors: Kluth P. , Johannessen B. , Giraud V. , Cheung A. , Glover C. J. , Azevedo G. de M. , Foran G. J. , Ridgway M. C.
Published: October 2004

Au nanocrystals (NCs) fabricated by ion implantation into thin SiO2 and annealing were investigated by means of extended x-ray absorption fine structure (EXAFS) spectroscopy and transmission electron microscopy. A bond length contraction was observed and can be explained by surface tension effects in a simple liquid-drop model. Such results are consistent with previous reports on nonembedded NCs implying a negligible influence of the SiO2 matrix. Cumulant analysis of the EXAFS data suggests surface reconstruction or relaxation involving a further shortened bond length. A deviation from the octahedral closed shell structure is apparent for NCs of size 25Å.
Computing the m=1 diocotron frequency via an equilibrium calculation in non-neutral plasmas
Authors: Spencer Ross L.
Published: October 2004

The m=1 diocotron mode in non-neutral plasmas has long been thought of as a shifted equilibrium, and its frequency has been approximately calculated in this way by Fine and Driscoll [Phys. Plasmas 5, 601 (1998)]. This article shows that this idea can be coupled with a standard axisymmetric equilibrium calculation on a grid to calculate the frequency of this mode to very high precision including both finite-length and thermal effects, provided that the Debye length is small enough. As the Debye length begins to approach the plasma size not only does the shifted equilibrium calculation fail to predict correctly the frequency of the mode, but the idea that the mode is a simple shift of the original equilibrium also becomes invalid.
Long-distance propagation of intense short laser pulse in air
Authors: Yu Wei , Yu M. Y. , Zhang J. , Qian L. J. , Yuan X. , Lu P. X. , Li R. X. , Sheng Z. M. , Liu J. R. , Xu Z. Z.
Published: October 2004

Long-distance propagation of intense laser pulse in air is reconsidered analytically by generalizing the analogy between the laser spotsize and the orbit of a classical particle. It is shown that multiphoton ionization introduces unique features to the laser-air interaction, thereby enabling the long-distance behavior. Several interesting characteristics of the latter are pointed out.
Fragile PT-symmetry in a solvable model
Authors: Znojil Miloslav
Published: October 2004

One of the simplest pseudo-Hermitian models with real spectrum (viz., square-well on a real interval I of coordinates) is re-examined. A PT-symmetric complex deformation C of I is introduced and shown tractable via an innovated approach to matching conditions. The result is surprising: An arbitrarily small deformation I→C implies a sudden collapse (i.e., the spontaneous PT-symmetry breaking) of virtually all the spectrum (i.e., up to its low-energy part).
Photodegradation of porous silicon induced by photogenerated singlet oxygen molecules
Authors: Kovalev D. , Gross E. , Diener J. , Timoshenko V. Yu. , Fujii M.
Published: October 2004

We report on the mechanism of photodegradation of porous silicon luminescence in ambient containing molecular oxygen. Energy transfer from excitons confined in silicon nanocrystallites to molecular oxygen results in the generation of highly chemically reactive singlet oxygen molecules. The subsequent interaction of singlet oxygen molecules with the hydrogenated surface of silicon nanocrystals results in its photooxidation and the creation of additional nonradiative defects, i.e., the luminescence fatigue effect.
Epitaxial growth of Eu2O3 thin films on LaAlO3 substrates by polymer-assisted deposition
Authors: Lin Y. , Wang H. , Hawley M. E. , Foltyn S. R. , Jia Q. X. , Collis G. E. , Burrell A. K. , McCleskey T. M.
Published: October 2004

Eu 2 O 3 thin films were epitaxially grown on (001)LaAlO3(LAO) substrates using a polymer-assisted deposition technique. Microstructural studies by x-ray diffraction and transmission electron microscopy show that the films are epitaxial with an orientational relationship of (001)Eu2O3∥(001)LAO and [11¯0]Eu2O3∥[100]LAO. We have found a systematic change in the out-of-plane lattice parameter of Eu2O3(a⊥) with the annealing temperature, which is believed to be from different strain effects.
Ultra-low-frequency self-oscillation of photocurrent in InxGa1−xAs∕Al0.15Ga0.85As multiple-quantum-well p–i–n diodes
Authors: Satake A. , Tanigawa K. , Kimura T. , Fujiwara K. , Sano N.
Published: October 2004

We report an observation of ultra-low-frequency self-oscillation of photocurrent in InxGa1−xAs∕Al0.15Ga0.85As multiple-quantum-well p–i–n diodes. The photocurrent intensity shows self-oscillations with a characteristic frequency of ∼0.1Hz at low temperatures under reverse bias voltages. The photocurrent self-oscillation depends on applied bias voltage, temperature, illumination power, and indium content of quantum-well layers. These dependences indicate that the photocurrent self-oscillation is attributed to photogenerated carriers trapped in localized centers within InxGa1−xAs quantum-well regions.
Self-consistent simulation of quantum shot noise in nanoscale electron devices
Authors: Oriols X. , Trois A. , Blouin G.
Published: October 2004

An approach for studying shot noise in mesoscopic systems that explicitly includes the Coulomb interaction among electrons, by self-consistently solving the Poisson equation, is presented. As a test, current fluctuations on a standard resonant tunneling diode are simulated in agreement with previous predictions and experimental results. The present approach opens a new path for the simulation of nanoscale electron devices, where pure quantum mechanical and Coulomb blockade phenomena coexist.
Highly flexible transparent electrodes for organic light-emitting diode-based displays
Authors: Lewis Jay , Grego Sonia , Chalamala Babu , Vick Erik , Temple Dorota
Published: October 2004

Multilayer indium-tin-oxide (ITO)–Ag–ITO stacks were evaluated as transparent conductors for flexible organic light-emitting diode (OLED) displays. The ITO–metal–ITO (IMI) samples exhibited significantly reduced sheet resistance over ITO and greater than 80% optical transmission. The IMI films deposited on plastic substrates showed dramatically improved mechanical properties when subjected to bending both as a function of radius of curvature as well as number of cycles to a fixed radius. OLEDs were fabricated on both ITO and IMI anodes, and the devices with IMI anodes showed improved performance at current densities greater than 1mA∕cm2 due to the improved conductivity of the anode.
Mechanical aspects of epitaxial ferroelectric Pb(Zr0.5Ti0.5)O3 films investigated by nanoindentation methods and piezoresponse force microscopy
Authors: Liu D. , White K. W.
Published: October 2004

Mechanical behaviors of a lead zirconium titanate (PZT) thin film are investigated using a unique combination of nanoindentation methods and piezoresponse force microscopy (PFM) in various domain areas, following local domain pattern writing. The interaction between the ferroelectric domain character and the mechanical behavior is mapped using PFM for subsequent nanoindentation. Significant anisotropic behaviors between (100) and (001) domains are observed. An anomalous increase of indentation elastic modulus in the region near a domain wall is observed.
A model for asymmetric giant magnetoimpedance in field-annealed amorphous ribbons
Authors: Buznikov N. A. , Kim CheolGi , Kim Chong-Oh , Yoon Seok-Soo
Published: October 2004

A phenomenological model for the asymmetric giant magnetoimpedance (GMI) in field-annealed amorphous ribbons is developed. The effect of a surface crystalline layer on the GMI response is described in terms of an effective bias field appearing due to a coupling between the crystalline layer and amorphous phase. It is shown that the presence of the bias field changes drastically the GMI profile. At low frequencies, the domain-walls motion leads to a steplike change in the GMI response. At high frequencies, the domain-walls motion is damped, and the GMI profile exhibits asymmetric two-peak behavior. The calculated dependences are shown to be in a qualitative agreement with results of experimental studies of the asymmetric GMI in field-annealed Co-based amorphous ribbons.
Mechanism of apatite formation on hydrogen plasma-implanted single-crystal silicon
Authors: Liu Xuanyong , Fu Ricky K. Y. , Chu Paul K. , Ding Chuanxian
Published: October 2004

Hydrogen is implanted into single-crystal silicon wafers using plasma ion immersion implantation to improve the surface bioactivity and the mechanism of apatite formation is investigated. Our micro-Raman and transmission electron microscopy results reveal the presence of a disordered silicon surface containing Si–H bonds after hydrogen implantation. When the sample is immersed in a simulated body fluid, the Si–H bonds on the silicon wafer initially react with water to produce a negatively charged surface containing the functional group (Si–O−) that subsequently induces the formation of apatite. A good understanding of the formation mechanism of apatite on hydrogen implanted silicon is not only important from the viewpoint of biophysics but also vital to the actual use of silicon-based microchips and MEMS inside a human body.
High piezoelectric response in polar-axis-oriented CaBi4Ti4O15 ferroelectric thin films
Authors: Fu Desheng , Suzuki Kazuyuki , Kato Kazumi
Published: October 2004

We report on the piezoelectric properties of polar-axis-oriented CaBi4Ti4O15 films detected by atomic force microscope (AFM). The sol-gel-derived films onto Pt foil show excellent switching properties, and can be uniformly polarized over large areas with a conductive AFM tip. The films have an extremely high piezoelectric coefficient of d33, and a value of 180pm∕V has been detected. These results indicate that the oriented bismuth-layered films can be used as the lead-free piezoelectrics.
Spin injection from Fe3Si into GaAs
Authors: Kawaharazuka A. , Ramsteiner M. , Herfort J. , Schönherr H.-P. , Kostial H. , Ploog K. H.
Published: October 2004

We demonstrate room-temperature spin injection from the epitaxially grown ferromagnetic metal Fe3Si into the semiconductor GaAs. The injection efficiency is comparable to values previously obtained for the Fe∕GaAs and MnAs∕GaAs hybrid systems using the emission of similar (In,Ga)As∕GaAs light-emitting diodes for the detection of spin polarization. The temperature dependence of the detected polarization is explained by taking into account spin relaxation inside the semiconductor device.
Oxygen transport and incorporation mechanisms in the dry thermal oxidation of 6H-SiC
Authors: Radtke C. , Baumvol I. J. R. , Ferrera B. C. , Stedile F. C.
Published: October 2004

Thermal oxidation of 6H-SiC was investigated by means of isotopic tracing and narrow nuclear resonant reaction profiling techniques. The mechanisms of oxygen transport and incorporation were accessed by sequential oxidations in dry O2 enriched or not in the O18 isotope and subsequent determinations of the O18 profiles. After sequential O216∕O218 or O218∕O216 oxidations of SiC, the O18 profiles were seen to be markedly different from those observed in Si oxidation, which led to the identification of different mechanisms of oxygen incorporation and transport. The gradual nature of the SiO2∕SiC interface was also evidenced by the O18 depth distributions in samples oxidized in a single step in O18-enriched O2. A probable explanation for this gradual SiO2∕SiC interface is shown to be the formation of C clusters during oxidation.
Size effect on Young’s modulus of thin chromium cantilevers
Authors: Nilsson S. G. , Borrisé X. , Montelius L.
Published: October 2004

Thin chromium cantilevers with sub-100nm thickness have been characterized by an atomic force microscope operating in contact mode. A continuous determination of the local mechanical properties at all lengths was accomplished by applying force along the length of the cantilevers. The result show a decrease of the Young’s modulus as the cantilevers get thinner.
Effects of exciton–biexciton coherent coupling on exciton absorption in quantum dots
Authors: Gotoh Hideki , Kamada Hidehiko , Saitoh Tadashi , Ando Hiroaki , Temmyo Jiro
Published: October 2004

We report unusual excitonic absorption spectra with dip-shaped structures caused by exciton–biexciton coherent interactions in quantum dots. The exciton absorption spectrum is measured with the micro-photoluminescence excitation technique in a single InGaAs quantum dot. The spectrum changes from Lorenztian-shaped to dip-shaped with increasing excitation intensity. A theoretical analysis with the density matrix method reveals that exciton–biexciton coherent interactions create dressed states in the exciton–biexciton system and lead to the unusual absorption spectra.
Spatial variation of luminescence from AlGaN grown by facet controlled epitaxial lateral overgrowth
Authors: Bell A. , Liu R. , Parasuraman U. K. , Ponce F. A. , Kamiyama S. , Amano H. , Akasaki I.
Published: October 2004

Interesting phenomena have been observed in the epitaxial lateral overgrowth of AlxGa1−xN alloys using facet control on serrated GaN templates. A complex microstructure is observed that involves misfit dislocation arrays that are closely related to regions with significantly large variations in composition. The dislocations are on inclined planar boundaries and result from basal-plane slip, which is allowed in this inclined facet geometry. The spatial variation of the aluminum composition in the overgrowth region is determined by cathodoluminescence spectroscopy and ranges from x=0.06to0.27, for constant growth conditions that after planarization result in a uniform composition at x=0.16. These results indicate that aluminum incorporation depends significantly on the growth direction with marked preference for facets parallel to the basal plane.
Highly coercive electrodeposited FePt films by postannealing in hydrogen
Authors: Leistner K. , Thomas J. , Schlörb H. , Weisheit M. , Schultz L. , Fähler S.
Published: October 2004

The properties of electrodeposited films subsequently annealed in H2 are reported and compared with those of vacuum-annealed samples. Annealing in hydrogen reduces the oxygen content incorporated during electrodeposition, resulting in significantly higher magnetization values. Phase formation is enhanced by hydrogen and L10 ordering starts at temperatures as low as 350°C. In addition, grain growth is hindered. These effects contribute to the high coercivity of 1.1T achieved after annealing at 600°C in H2.
Efficient Raman amplification in silicon-on-insulator waveguides
Authors: Liang T. K. , Tsang H. K.
Published: October 2004

We describe a silicon-on-insulator waveguide Raman amplifier which achieves a large fiber-to-fiber optical gain of 6.8dB using stimulated Raman scattering in a 1.7-cm-long silicon waveguide. By using picosecond pulse pumping at 1557.4nm wavelength, high net optical gain at the first-order Stokes wavelength of 1694.6nm was measured. The optical loss from two-photon absorption generated free carriers was reduced by using a low pulse duty cycle and picosecond pulse pumping.
Self-consistent determination of the generation rate from photoconductance measurements
Authors: Trupke T. , Bardos R. A.
Published: October 2004

The determination of effective excess carrier lifetimes from photoconductance measurements generally requires knowledge of the absolute generation rate within a sample. Measurements of the generation rate typically involve measurement of the sample absorption spectrum and of the incident light intensity. This letter presents an experimental and analytical method by which both the effective lifetime and the generation rate can be self-consistently determined. The method involves only relative measurements of the generation rate, greatly simplifying the experimental requirements. Good agreement is found experimentally between the results achieved using this method and results from transient photoconductance measurements.
Electrochemical nanopatterning of Ag on solid-state ionic conductor RbAg4I5 using atomic force microscopy
Authors: Lee Minhwan , O’Hayre Ryan , Prinz Fritz B. , Gür Turgut M.
Published: October 2004

This report introduces an electrochemical nanopatterning technique performed under ambient conditions without involving a liquid vessel or probe-to-sample material transfer. Patterning is accomplished by solid-state electrochemical nanodeposition of Ag clusters on the surface of the solid ionic conductor RbAg4I5 using an atomic force microscopy probe. Application of negative voltage pulses on the probe relative to an Ag film counter electrode on an RbAg4I5 sample induces nanometer-sized Ag deposition on the ion conductor around the probe. The patterned Ag particles are 0.5–70nm high and 20–700nm in diameter. The effect of the amplitude and duration of bias voltage on the size and shape of deposited Ag clusters is also shown.
Strong affinity of hydrogen for the GaN(000-1) surface: Implications for molecular beam epitaxy and metalorganic chemical vapor deposition
Authors: Northrup J. E. , Neugebauer J.
Published: October 2004

The stabilities of clean and hydrogen covered GaN(000-1) surfaces are determined using density functional theory together with a finite temperature thermodynamics approach. Hydrogen has an extremely high affinity for the N-face surface: Even under ultrahigh vacuum conditions as realized in molecular beam epitaxial growth, with a residual hydrogen pressure of 10−12atm, the hydrogen terminated surface is, for very N-rich conditions, more stable than any clean surface. A transition to a surface covered by a Ga adlayer is predicted to occur as the Ga chemical potential increases. In typical metalorganic chemical vapor deposition conditions the (000-1) surface is predicted to be covered by 0.75 monolayers of hydrogen. The slower growth rate on the (000-1) surface in comparison to the (0001) surface is attributed to low adsorption of N on the H-covered (000-1) surface.
Ultrabroadband detection of multi-terahertz field transients with GaSe electro-optic sensors: Approaching the near infrared
Authors: Kübler C. , Huber R. , Tübel S. , Leitenstorfer A.
Published: October 2004

Field-resolved detection of ultrabroadband infrared pulses is implemented with GaSe crystals. Via phase matching, we extend the detectable frequency range toward the near infrared (λ=2.5μm) and directly record transform-limited pulses as short as 28fs with a 3dB bandwidth of 41THz. The continuous tunability of the center frequency over a wide interval ranging from 31THz to the far-infrared is demonstrated using thick sensors.
Optical properties of erbium-implanted porous silicon microcavities
Authors: Reece P. J. , Gal M. , Tan H. H. , Jagadish C.
Published: October 2004

We have used ion implantation for erbium doping of mesoporous silicon microcavities. Optically active erbium-doped microcavities with Q factors in excess of 1500 have been demonstrated. We observed strong modification of the emission properties of the erbium in the microcavity with an accompanying cavity enhancement factor of 25. In addition, power- and temperature-dependent photoluminescence measurements indicate that erbium-implanted porous silicon has excitation mechanism very similar to that of erbium in a crystalline silicon host.
Textured nano-agglomerates embedded in the thin film of La0.8Sr0.2MnO3
Authors: Zhu Y. L. , Wu B. , Ma X. L. , Li D. X. , Lu H. B. , Chen Z. H. , Yang G. Z.
Published: October 2004

We have observed nano-scale chemical composition separation in the thin film of La0.8Sr0.2MnO3 by means of high-angle-angular-dark-field imaging, elemental mapping, and composition line-scanning in a transmission electron microscope. It is found that highly dense and dimensionally uniform nano-agglomerates are embedded in the film. The ratio of Mn∕La in the nano-agglomerates is fluctuated and generally much higher than that in their surrounding medium. Such compositional inhomogeneities result in a textured microstructure, which is one of the most important parameters for tunning electronic properties in the colossal magnetoresistance oxides.
Evolution of stress in GaN heteroepitaxy on AlN∕Si(111): From hydrostatic compressive to biaxial tensile
Authors: Krost A. , Dadgar A. , Bläsing J. , Diez A. , Hempel T. , Petzold S. , Christen J. , Clos R.
Published: October 2004

The initial steps of GaN growth on an AlN buffer layer on Si(111) substrates by metalorganic vapor phase epitaxy were investigated using field emission scanning electron microscopy, micro-photoluminescence, as well as by conventional and grazing incidence x-ray diffraction. A series of GaN layers was grown for various times ranging from 7.5 s to several minutes, doubling the growth time for each step. The AlN buffer layer is noncontinuous and consists of (0001)-oriented AlN islands with a mean diameter of about 50 nm. On top of these nucleation centers three-dimensional growth of GaN was observed. With increasing growth times up to 30 s these islands further expanded and their distribution became more homogeneous. At 60 s coalescence started with homogeneously distributed islands, and after 120 s the layer was fully coalesced. The layers grown for 7.5 and 15 s are under a high compressive hydrostatic pressure, which might be enhanced by the lattice mismatch between AlN and GaN. For longer growth times a biaxial tensile stress is observed. The occurrence of the biaxial tensile stress correlates with the onset of island coalescence. The x-ray results are in agreement with low-temperature optical measurements showing a consistent energy shift of the near band gap luminescence and longitudinal optical Raman modes with respect to relaxed GaN.
Efficient ultraviolet electroluminescence from a Gd-implanted silicon metal–oxide–semiconductor device
Authors: Sun J. M. , Skorupa W. , Dekorsy T. , Helm M. , Rebohle L. , Gebel T.
Published: October 2004

Strong ultraviolet electroluminescence with an external quantum efficiency above 1% is observed from an indium-tin oxide/SiO2:Gd∕Si metal–oxide–semiconductor structure. The SiO2:Gd active layer is prepared by thermal oxidation followed by Gd+ implantation and annealing. The electroluminescence spectra show a sharp peak at 316nm from the P7∕26 to S7∕28 transition of Gd3+ ions. Micrometer-sized electroluminescent devices are demonstrated.
Compressibility and pressure-induced phase transformation of Ti3GeC2
Authors: Wang Zhongwu , Zha C. S. , Barsoum M. W.
Published: October 2004

In order to explore the large shear-strain-induced polymorph, α-Ti3GeC2 polycrystals were investigated by using a synchrotron radiation source to 64GPa under nonhydrostatic state. Upon compression to 26.6GPa, α-Ti3GeC2 starts to transform to β-Ti3GeC2. As compared to α-Ti3GeC2, the cell parameter a of β-Ti3GeC2 is slightly shorter, and both c and c∕a larger. These two polymorphs exhibit similar compressibility. The bulk modulus is calculated to be 179(±10)GPa at a fixed K′=4.0. This is lower than that of Ti3SiC2, and close to that of Ti3Si0.5Ge0.5C2. The compressibilities of these two Ti3GeC2 polymorphs do not display an apparent anisotropy, and differ from the large anisotropies observed from Ti3SiC2 and Ti3Si0.5Ge0.5C2.
Three-dimensional mapping of the strain anisotropy in self-assembled quantum-wires by grazing incidence x-ray diffraction
Authors: Gutiérrez H. R. , Magalhães-Paniago R. , Bortoleto J. R. R. , Cotta M. A.
Published: October 2004

Three-dimensional strain mapping of InAs self-assembled nanowires on an InP substrate using grazing incidence x-ray diffraction is reported. A remarkable anisotropy was observed for the strain components, parallel [−220] and perpendicular [220] to the wire axis. The highest strain relaxation was measured along the [220] direction. The relationship between the interatomic distances along the [−220] and [220] directions, for each z position (height) in the nanostructure, was obtained by angular scans in the vicinity of the (040) reciprocal lattice point.
A potential low-temperature oxide-ion conductor: La2−xBaxMo2O9
Authors: Basu S. , Devi P. Sujatha , Maiti H. S.
Published: October 2004

An oxide ion conducting material, La1.94Ba0.06Mo2O9, with ionic conductivity of the order of 0.084S∕cm at 800°C in air was prepared by a citrate-nitrate auto-ignition process. A 3% Ba doping has suppressed the resistive transition of unsubstituted La2Mo2O9, which in turn stabilized the high-temperature cubic phase at room temperature as confirmed from x-ray diffraction, differential thermal analysis, and dilatometric studies. Impedance measurements on sintered La1.94Ba0.06Mo2O9 further lend strong support that a small amount of Ba doping has increased the overall conductivity of the parent compound La2Mo2O9 to a notable extent both at low and high temperatures.
Parametric fluorescence based on the third-order susceptibility χ(3) in high nonlinearity fiber
Authors: Ni Yi , Wang Qing , Liu Xiaoming , Peng Jiangde , Zhou Bingkun
Published: October 2004

Parametric fluorescence based on the third-order susceptibility χ(3) in high nonlinearity fiber (HNLF) is quantitatively analyzed by the semiclassical method. In an all-fiber setup consisting of 1.45km HNLF with nonlinear coefficient γ=12W−1km−1, parametric fluorescence power of 360nW and conversion efficiency as high as 6×10−6W∕W has been measured with pump power of 57mW. The measured parametric fluorescence spectrum has good symmetry.
A controllable nanomechanical memory element
Authors: Badzey Robert L. , Zolfagharkhani Guiti , Gaidarzhy Alexei , Mohanty Pritiraj
Published: October 2004

We report the realization of a completely controllable high-speed nanomechanical memory element fabricated from single-crystal silicon wafers. This element consists of a doubly clamped suspended nanomechanical beam structure, which can be made to switch controllably between two stable and distinct states at a single frequency in the megahertz range. Because of their submicron size and high normal-mode frequencies, these nanomechanical memory elements offer the potential to rival the current state-of-the-art electronic data storage and processing.
Schottky diode characteristics of electrodeposited Au∕n-Si(111) nanocontacts
Authors: Hugelmann M. , Schindler W.
Published: October 2004

Au ∕ n - Si ( 111 ) contacts with interface areas in the range of 10−12cm2 have been fabricated at the solid/liquid interface by electrochemical Au nucleation onto n-Si(111):H substrates. The contacts show a Schottky diode behavior with current densities much higher than expected from thermionic emission theory. The applied sophisticated in situ measurement technique allows, in general, in situ studies of electronic properties at any (semi-) conducting nanostructure at solid/liquid interfaces under well-defined conditions.
Surface tension of superheated and undercooled liquid Co–Si alloy
Authors: Wang H. P. , Yao W. J. , Cao C. D. , Wei B.
Published: October 2004

The surface tension of superheated and undercooled liquid Co 25wt.% Si alloy was measured by an electromagnetic oscillating drop method. The experimental temperature regime was from 1384 to 2339K and a maximum undercooling of 223K (0.14TL) was achieved. The surface tension of liquid Co 25wt.% Si alloy is 1.604Nm−1 at the liquidus temperature of 1607K, and its temperature coefficient is −4.0×10−4Nm−1K−1. On the basis of previous research results of pure Co and Si, an expression is developed to predict the surface tension of binary Co–Si alloy system. The other thermophysical properties, such as the viscosity, the solute diffusion coefficient, and the density of liquid Co 25wt.% Si alloy are also derived by the relevant theoretical models.
Fabrication and characterization of a biologically sensitive field-effect transistor using a nanocrystalline diamond thin film
Authors: Yang Wensha , Hamers Robert J.
Published: October 2004

We report the fabrication and characterization of a biologically sensitive field-effect transistor (Bio-FET) using a nanocrystalline diamond thin film. Biomolecular recognition capability was provided by linking human immunoglobulin G (IgG) to the diamond surface. Electrical measurements reveal behavior characteristic of field-effect transistors. The biomolecular recognition and specificity characteristics were tested using the two antibodies anti IgM and anti-IgG. Electrical measurements show that the Bio-FET device made on an IgG-modified diamond exhibits a response specific to the anti-IgG antibody. Our results demonstrate the ability to fabricate a bio-FET device using a biologically modified diamond thin film.
Modeling and performance of vanadium–oxide transition edge microbolometers
Authors: de Almeida L. A. L. , Deep G. S. , Lima A. M. N. , Khrebtov I. A. , Malyarov V. G. , Neff H.
Published: October 2004

The performance of a VO2 thin-film microbolometer has been investigated. The device is operated within 35°C<T<60°C, in the hysteretic metal-insulator transition region. An algebraic hysteresis model has been used to model the resistance-temperature characteristic of the sensor. It accurately describes the resistance versus temperature characteristics of the material. Employing this model, and in conjunction with established bolometer theory, the responsivity of a VO2 film is calculated and compared with experimental data. Superior performance of the device is achievable under conditions of single pulse incident radiation where the operating point remains on the major hysteresis loop. This results in a pronounced responsivity peak within the center of the metal-insulator transition. Continuous periodic excitation, in contrast, leads to a steadily decreasing and much lower sensitivity at higher temperature, due to the formation of minor hysteresis loops and the loop accommodation process.