bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ferro–antiferromagnetic coupling and enhancement of magnetoresistance in La0.7Ca0.3MnO3/LaMnO3 composites
Authors: Zhu Y. D. , Li Xing‐Ao , Liao H. H. , Yang Q. 
Published: December 2008

AbstractThe samples with the nominal composition of (La0.7Ca0.3MnO3)1–x /(LaMnO3)x with x = 0.00, 0.05, 0.15 and 0.25 were fabricated using traditional solid‐state reaction method. The electrical‐magnetic transport behavior and magnetoresistance (MR) were studied for the composites in magnetic fields H = 0.3 T, 3 T. Experimental results show that with the increasing of LaMnO3 (LMO) content x, the metal–insulator (M–I) transition temperature TP shifts to lower temperature and the resistivity increases sharply in zero magnetic field. Meanwhile, a significant enhancement in MR is observed for the composites, especially in the low temperature range (below TP). Specially, the maximum MR at 3 T increased from 35% for the pure La0.7Ca0.3MnO3 (LCMO) to 92% for the sample with x = 0.25. We suggest that such enhancement in MR is attributed to the strong ferro–antiferromagnetic coupling effects in the composite system, which increase the magnetic disorder at the grain surface and boundary, will improve the spin‐polarized tunneling process of the conducting electron between adjacent grains, and thus enhance the MR effect. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the improvement of the anode/organic material interface in organic solar cells by the presence of an ultra‐thin gold layer
Authors: Kouskoussa B. , Morsli M. , Benchouk K. , Louarn G. , Cattin L. , Khelil A. , Bernède J. C. 
Published: December 2008

AbstractThe energy conversion efficiency of organic solar cells based on simple electron donor/electron acceptor heterojunction has been studied as a function of the interface anode/electron donor. The anode is fluorine doped tin oxide film. It is shown that the solar cell efficiency increases when a metal ultra thin layer is introduced between the anode and the electron donor. Experimental and theoretical studies show that the work function value of the metal is one of the main factors which allow improving the organic solar cells performances, via better hole collection efficiency. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dielectric relaxation in lead‐free perovskite Ba(Bi1/2Nb1/2)O3
Authors: Prasad K. , Bhagat S. , Nath K. Amar , Choudhary S. N. , Yadav K. L. 
Published: December 2008

AbstractA new lead‐free perovskite ceramic Ba(Bi1/2Nb1/2)O3 was prepared by a conventional ceramic technique at 1185 °C in oxygen atmosphere. X‐ray diffraction analysis of the compound indicated the formation of a single‐phase monoclinic structure. Dielectric study revealed a diffuse phase transition at 340 °C. Cole–Cole analyses suggested the dielectric relaxation to be of non‐Debye type. Electric modulus studies supported the hopping type of conduction in Ba(Bi1/2Nb1/2)O3. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
GaN‐based vertical cavities with crack‐free high‐reflectivity patterned AlGaN/GaN distributed Bragg reflectors
Authors: Ni X. , Shimada R. , Kang T. D. , Leach J. H. , Özgür Ü. , Morkoç H. 
Published: December 2008

AbstractWe report on GaN‐based vertical cavities using crack‐free 40.5 pair of AlGaN/GaN distributed Bragg reflectors (DBRs) by employing a selective growth method to avoid wafer cracking that has been commonly observed in conventional planar Al(Ga)N/GaN DBRs. An Al0.46Ga0.54N/GaN DBR with ∼98% reflectivity was selectively grown with square patterns of up to 150 × 150 μm2 in size, which were separated from each other by 10 μm wide SiO2 mask stripes. Vertical cavity structures employing InGaN multiple quantum wells were grown on these crack‐free DBRs and capped with 8 pair dielectric SiO2/SiNx DBRs. Cavity mode centered at ∼400 nm was observed to have a quality factor of ∼100. The selective DBR and vertical cavity growth to eliminate crack formation appears very promising for the fabrication of nitride‐based vertical‐cavity surface emitting laser devices. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spatial features control of self‐organised tungsten nanowire arrays
Authors: Milenkovic Srdjan , Hassel Achim Walter 
Published: December 2008

AbstractSelf‐organised tungsten nanowire arrays were produced by a recently established templateless method. Control of spatial features such as diameter and spacing of nanowires was successfully achieved by changing the growth rate during directional solidification. An increase in the growth rate from 1.4 μm s–1 to 55.5 μm s–1 led to a decrease in the nanowire diameter from 560 to 290 nm and the spacing from 3.5 μm to 1.7 μm. The scaling laws of the variation in nanowire diameter and spacing with growth rate are quantitatively determined. Distribution of both, the diameter and the spacing around the average value were quite narrow. Potential applications of such self‐organised W nanowire arrays in nanotechnology are discussed. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Molecular dynamics simulation of annihilation of 60° dislocations in Si crystals
Authors: Meng Qingyuan , Wang Qingsheng 
Published: December 2008

AbstractThe annihilation of two 60° shuffle dislocations is studied via the molecular dynamics method. The Stillinger–Weber (SW) potential and environment‐dependent interatomic potential (EDIP) are used to describe the atomic interactions. The simulation results show that the complete annihilation of the 60° dislocations takes place only when the two dislocations lie on the same slip plane. The annihilation process may occur without external shear stress when the temperature is higher than a critical value. It is found that the critical temperature increases exponentially as a function of distance between the two dislocations. Also revealed in this simulation is an incomplete annihilation occurring when the distance between the slip planes of the two dislocations is less than about 1 nm. If the distance between the two slip planes is larger than about 1 nm, the dislocations will glide on their own slip planes as if no interaction exists between them. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Coherence properties and dynamical photon correlations of quantum‐dot‐based microcavity lasers
Authors: Wiersig J. , Gies C. , Jahnke F. 
Published: December 2008

AbstractMicrocavity lasers have attracted considerable attention due to their potential for ultralow threshold lasing. An important parameter to characterize lasers is the spontaneous emission factor β, defined as the ratio of the spontaneous emission into the laser mode to the total spontaneous emission. When β approaches unity in devices with hight cavity quality and low mode volume, the input‐output curve cannot be used to determine the laser threshold unambiguously. To describe the emission properties of microcavity lasers, we investigate the first‐ and second‐order photon correlation functions. Even in the case of β = 1 we find a strong increase of the coherence time and indications of a gradual transition from Bose–Einstein to Poisson statistics. We also study the decay of first‐ and second‐order photon correlations. The detailed characterization of microcavity lasers is particularly important for potential applications in quantum information technologies. Our results are obtained from a microscopic theory for quantum‐dot emitters as active material. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Control of single quantum dot emission characteristics and fine structure by lateral electric fields
Authors: Ulrich S. M. , Hafenbrak R. , Vogel M. M. , Wang L. , Rastelli A. , Schmidt O. G. , Michler P. 
Published: December 2008

AbstractThe spontaneous emission characteristics of individual self‐assembled (In,Ga)As/GaAs quantum dots have been investigated under the application of a tunable electric field in the lateral growth plane. For the neutral excitonic and bi‐excitonic as well as a singly‐charged (trionic) QD carrier configuration, similar quantum‐confined Stark effects could be observed, thus enabling a direct and comparative determination of corresponding polarizability values α. In addition we have applied a refined detection technique of high‐resolution Fabry–Pérot interferometry on single QDs to investigate the anisotropy‐induced excitonic fine structure and to monitor its tunability under a lateral electric field. Whereas most quantum dots reveal an oscillatory‐type modulation and partial reduction in fine structure under the applied field, we also demonstrate the case of a selected QD where the initial fine structure could even be reversibly tuned down to zero. This fine structure tunability of single QDs represents an essential prerequisite for the realization of individually controlled entangled photon sources in the future. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic properties and phase transitions in Si, ZnSe, and GaAs under pressure cycling up to 20–30 GPa in a high‐pressure cell
Authors: Ovsyannikov Sergey V. , Shchennikov Vladimir V. , Misiuk Andrzej , Komarovsky Ivan A. 
Published: December 2008

AbstractAn automated high‐pressure setup employing anvil‐type cells is applied for investigation of phase transitions and elec‐ tronic properties (the thermoelectric power (Seebeck effect), the electrical resistivity) of silicon, zinc selenide and gal lium arsenide under pressure cycling within the range of 0–20(30) GPa. The “correlation” dependencies of a pressure value of the semiconductor–metal transition in Czochralski‐grown silicon (Cz‐Si) on the concentrations of both carriers and residual interstitial oxygen are discussed. In all Si samples a decompression of the high‐pressure metal phase produces the semimetal p‐type phases: the rhombohedral r8 (Si‐XII) and the body‐centred cubic bc8 (Si‐III) lattices. Re‐ pressurization cycles reveal two features in the semimetal phase, near 2 GPa and 5 GPa. The transitions into the metal phase at higher pressure resemble those in pristine silicon. For ZnSe and GaAs, it is found that decompression from the high‐pressure phases (NaCl and Cmcm, respectively) can follow different paths, producing the zincblende, the cinnabar and the wurtzite lattices. Advantages of the characterization method are discussed, in comparison with both the traditional techniques (X‐ray diffraction, Raman spectroscropy, etc.) and the more recent ones (such as nanoindentation). (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Polarized Raman study of self‐assembled Ge/Si dots under hydrostatic pressure
Authors: Reparaz J. S. , Bernardi A. , Goñi A. R. , Alonso M. I. , Garriga M. 
Published: December 2008

AbstractWe have studied the correlation between the morphology of Si‐capped Ge islands grown on Si substrates and their vibrational properties as measured by Raman scattering at ambient and under high hydrostatic pressure. For this study we have grown by molecular beam epitaxy a sample that exhibits a size distribution with two distinct island types having different aspect ratios called pyramids and domes. In accordance, Raman spectra show a double‐peak structure at the frequencies of the Ge–Ge vibrational mode (∼300 cm–1) as well as for the Si–Ge mode (around 400 cm–1). Pairwise, different selection rules have been found for these modes depending upon the Raman polarization configurations, suggesting a correlation between both Ge dot sizes and the double peak structure in the Raman spectra. Finally, a different strain status of the dots was observed by studying the pressure coefficient of the Ge–Ge phonon mode, resulting in a value of 3.3 and 3.6 cm–1/GPa for pyramids and domes, respectively. The main conclusion of our work is that the double‐peak structure observed in Raman spectra is indicative of a bimodal dot size distribution in contrast with what is proposed in previous work within the so‐called core‐shell model [M. Y. Valakh et al., Nanotechnol. 16, 1464 (2005)]. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Study of the electronic properties of GaAs‐based atomic layer doped field effect transistor (ALD‐FET) under the influence of hydrostatic pressure
Authors: Martínez‐Orozco J. C. , Rodríguez‐Vargas I. , Duque C. A. , Mora‐Ramos M. E. , Gaggero‐Sager L. M. 
Published: December 2008

AbstractBased on a Thomas–Fermi envelope function scheme we perform the calculation of the electronic structure of a GaAs atomic layer doped field effect transistors (ALD‐FET). We calculate the electronic structure for the device as a function of the involved parameters, in particular we study the effects of the hydrostatic pressure onto the electronic level structure in order to investigate the formation of high conductivity electron channels in such devices. We consider the pressure‐induced Γ–X crossover within the conduction band as a possible effect causing the enhancement of the associated two‐dimensional carrier densities. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Scheme for coherently quenching resonant current in a three‐level quantum dot energy level mixer
Authors: Austing D. G. , Payette C. , Nair S. V. , Yu G. , Gupta J. A. , Partoens B. , Amaha S. , Tarucha S. 
Published: December 2008

AbstractWe outline a scheme to create a “dark” state by three‐level mixing that is potentially a useful tool for quantum coherent transport. Magnetic‐field‐induced intra‐dot level mixing can lead to rich quantum superposition phenomena between three approaching single‐particle states in a quantum dot when probed by the ground state of an adjacent weakly coupled quantum dot in the single‐electron resonant tunnelling regime. The mixing relies on non‐negligible anharmonicity and anisotropy in confining potentials of realistic quantum dots. Anti‐crossing and transfer of strengths between resonances can be understood with a simple coherent level mixing model. Superposition can lead to the formation of a dark state by complete cancellation of an otherwise strong resonance. This is an all‐electrical analogue of coherent population trapping seen in three‐level‐systems from quantum and atom optics. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On dot and out of dot electrical characteristics of silicon oxide nanodots patterned by scanning probe lithography
Authors: Hutagalung Sabar D. , Darsono Teguh 
Published: December 2008

AbstractSilicon oxide nanodot arrays were grown on pre‐cleaned silicon (100) substrate by scanning probe nanolithography. In this study, a conductive AFM was used to fabricate nanoscale oxide dots in humidity controlled environment. The AFM is equipped with a nanotechnology software package providing the control of tip‐sample voltage and tip motion according to pre‐designed patterns. The surface topography and size of obtained patterns (diameter and height) were investigated by a noncontact AFM mode. A series of five silicon oxide nanodot array with diameter in the range of 146.05‐247.65 nm and height 2.14‐4.87 nm had been successfully fabricated. Meanwhile, a contact AFM mode was used to investigate the localized I‐V characteristics on the dots and out of dot position. It was found, the on dot characteristics are highly nonohmic due to potential barrier interface between silicon oxide and silicon substrate. However, the out of dot characteristic is linear indicates an ohmic contact between AFM tip and sample. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Towards a single‐photon all‐optical transistor
Authors: Dawes Andrew M. C. 
Published: December 2008

AbstractThe Expert Opinion is written by a distinguished scientist and presents his personal view on important and relevant new results of research, highlighting their significance and putting the work into perspective for a broader audience. Please send comments to pss.rapid@wiley‐vch.de or to the author. The text by Andrew M. C. Dawes refers to the Rapid Research Letter by S. Schumacher et al., published in this issue of Phys. Status Solidi RRL 3, 10 (2009). (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electrospray ionization tandem mass spectrometric analysis of ent‐6,7‐seco‐kaurane diterpenoids from the Isodon species
Authors: Zhou Yan , Yang Bin‐Li , Yang Jing , Huang Sheng‐Xiong , Sun Han‐Dong , Xu Hong‐Xi , Ding Li‐Sheng 
Published: December 2008

AbstractElectrospray ionization tandem mass spectrometry (ESI‐MSn) using an ion trap instrument and accurate mass measurement on a quadrupole time‐of‐flight (Q‐TOF) mass spectrometer has aided the structural characterization and differentiation of the enmein and spiro‐lactone types of ent‐6,7‐seco‐kaurane diterpenoids from Isodon species. The mass spectral fragmentation data from both techniques was compared to obtain the mass spectrometric fragmentation pathways of the ent‐6,7‐seco‐kaurane diterpenoids with high confidence. The analysis revealed that losses of CH2O and CO2 are the predominant process for the enmein type of ent‐kauranes in negative ion mode, and the loss of CO2 is typical for the spiro‐lactone type in positive ion mode. In addition, compounds of the spiro‐lactone type with a conserved core structure but different substituent groups, such as acetyl, hydroxyl, and aldehyde moiety, resulted in diagnostic product ions by means of successive losses of AcOH, H2O, and CO, respectively. The fragmentation knowledge will facilitate the analysis and identification of the ent‐6,7‐seco‐kauranes in future plant research. Copyright © 2008 John Wiley & Sons, Ltd.
FBT: an efficient traceback scheme in hierarchical wireless sensor network
Authors: Cheng Bo‐Chao , Chen Huan , Liao Guo‐Tan 
Published: December 2008

AbstractWith limited resource constraints, wireless sensor networks (WSNs) pose unique technical challenges: WSNs are vulnerable to DoS/DDoS attacks that can easily exhaust rare available resources to prevent execution of their expected functions. Reconstructing the attacking path and locating the attacking source are challenging tasks in the traceback research areas. In conventional IP networks, probabilistic packet marking (PPM) schemes are among the widely used traceback algorithms. However, due to their high convergence times, conventional PPM schemes are not enough for the need for quick and accurate traceback in WSNs. Because marking probability assignment schemes have considerable influence on convergence time and performance, we place a particular emphasis on how to improve both easiness and efficiency for the marking probability assignment of the PPM. In this paper, we propose a novel traceback scheme, called fishbone traceback (FBT), which can be deployed in hierarchical WSN environments. FBT is designed based on the two‐layer labelling technique and a smart marking probability distribution function (MPDF). The use of two‐layer FBT labels is to derive the main branch (‘fish spine’) of the attacking path quickly, while the use of MPDF can greatly reduce the convergence time by integrating witha prioriinformation of hierarchical WSN topology. The FBT path reconstruction procedure is able to rebuild the spine path (for inter‐cluster traceback)viacluster head marking packets. It also reforms the details of the micro fishbone path (for intra‐cluster traceback) on‐demand within a cluster. Both numerical analysis and simulation results show that our solution has better performance in terms of shorter traceback convergence time. In particular, the proposed FBT also includes many salient features (such as the enhanced robustness of the traceback algorithm in case of multi‐attack and reusable spine path), which enable FBT to be a practical solution to the traceback problem in hierarchical WSNs. Copyright © 2008 John Wiley & Sons, Ltd.
Fast convergent key distribution algorithms using a dual quantum channel
Authors: Jin Di , Verma Pramode K. , Kartalopoulos Stamatios V. 
Published: December 2008

AbstractThis paper presents three new algorithms over a dual quantum channel to enhance the convergence speed of the key distribution process. The proposed algorithms effectively use a dual quantum channel between the communicating entities and, when combined with the proposed selection of the basis, improve the efficiency of the key distribution process as well as deter Eve. With the use of an initialization vector (IV), the proposed algorithm does not necessitate information exchange about the bases between Alice and Bob, thus removing the requirement of the availability of a two‐way conventional channel. Simultaneously, it allows the detection of the presence of Eve in real time. Copyright © 2008 John Wiley & Sons, Ltd.
Atomic‐level characterization of materials with core‐ and valence‐level photoemission: basic phenomena and future directions
Authors: Fadley Charles S. 
Published: December 2008

AbstractIn this overview, the basic concepts of core and valence photoelectron spectroscopy (photoemission), photoelectron diffraction, and photoelectron holography are introduced. Then some current developments in these techniques that should enhance their utility for atomic‐level characterization of new materials and surface chemical processes are discussed, including measurements with hard X‐ray excitation, standing‐wave excitation, and ambient pressures in the multi‐torr regime. Copyright © 2008 John Wiley & Sons, Ltd.
Chemical‐state‐resolved in‐depth profiles of gate‐stack structures on Si studied by angular‐dependent photoemission spectroscopy
Authors: Toyoda S. , Okabayashi J. , Oshima M. , Liu G. L. , Liu Z. , Ikeda K. , Usuda K. 
Published: December 2008

AbstractWe have investigated chemical‐state‐resolved in‐depth profiles of SiO2/SiN stack films using angular‐dependent photoemission spectroscopy and maximum‐entropy method (MEM). MEM enables to reproduce the gate‐stack structure from angular‐dependence of core‐level spectra, and it is utilized to determine atomic concentration of the interfacial layer. In‐depth profile of the SiO2/SiN stack film reveals that the SiO2layer is distributed in the surface region and that the SiN layer is partly oxidized, which is well related to nitrogen bonding states analyzed by angular‐dependence of N 1s core‐level spectra. Copyright © 2008 John Wiley & Sons, Ltd.
Characterization of atomic‐level plasmonic structures by low‐energy EELS
Authors: Nagao Tadaaki 
Published: December 2008

AbstractPlasmonic excitation in atomic‐level one‐dimensional (1D) structure is characterized by use of electron diffraction and electron scattering spectroscopy with highly collimated slow electron beam. The high momentum resolution of the technique unveils the presence of steeply dispersing plasmon dispersion of the atom chains in the infrared region that is usually smeared out as broad feature near the Bragg beams. Two different Au and In chain structures on stepped silicon surfaces are measured to show plasmon dispersion only along the chains, which indicates strong plasmon confinement in each chain. On the other hand, different slope of the plasmon dispersion are found, which is due to the difference in their 1D electronic band and chain width. Copyright © 2008 John Wiley & Sons, Ltd.