bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transient pump–probe measurements for polarized excitons in strained GaN epitaxial layers
Authors: Ishiguro T. , Toda Y. , Adachi S. , Arita M. , Arakawa Y. 
Published: June 2006

AbstractWe have studied exciton spin relaxation in strained GaN epilayers on various sapphire substrates using spindependent transient reflectivity and three‐pulse four‐wave mixing measurements. Strikingly fast exciton spin relaxation (<1 ps) at 10 K was observed in the lowest exciton level (A‐exciton) both in bulk and GaN layer on c‐sapphire. In contrast, the transient signals in the GaN layer on a‐sapphire show the break down of the spin polarization caused by the exchange interaction. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
In situ and ex situ grazing incidence diffraction anomalous fine structure study of GaN/AlN quantum dots
Authors: Coraux J. , Renevier H. , Proietti M. G. , Favre‐Nicolin V. , Daudin B. , Renaud G. 
Published: June 2006

AbstractWe report on a general method that takes advantage of the full capability of anomalous diffraction and can be applied to the challenging case of small size embedded nanostructures. We study in situ and ex situ GaN Quantum Dots (QDs) grown by Plasma Assisted Molecular Beam Epitaxy (PAMBE), and encapsulated by an AlN epilayer. We investigate the QD strain and composition that are related to size, morphology, and cap layer thickness by means of anomalous diffraction in grazing incidence. The X‐ray energy is tuned across the Ga K‐edge where the Ga atoms scattering power is strongly modified and diffraction becomes chemically selective, giving direct information on composition. Quantitative analysis of the oscillatory extended region above the edge gives information on composition and out‐of‐plane strain of the dots. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
New semiconductor alloy GaNAsBi with temperature‐insensitive bandgap
Authors: Yoshimoto Masahiro , Huang Wei , Feng Gan , Oe Kunishige 
Published: June 2006

AbstractGaNyAs1–x–yBix alloys were grown by molecular beam epitaxy (MBE). Successful incorporation of N and Bi atoms was confirmed and their concentration was evaluated by Rutherford backscattering spectroscopy (RBS) and secondary ion mass spectroscopy (SIMS). Single‐peak photoluminescence (PL) spectra were observed in the temperature range of 10–300 K. The PL peak energy of GaNyAs1–x–yBix alloy decreased with increasing GaBi and GaN molar fractions with redshift coefficients of ∼62 meV/%Bi and ∼130 meV/%N, respectively, at room temperature. The temperature dependence of the PL peak energy in the temperature range of 150–300 K is much smaller than the temperature dependence of the bandgap for InGaAsP. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural evaluation of GaN/sapphire grown by epitaxial lateral overgrowth by X‐ray microdiffraction
Authors: Drakopoulos M. , Laügt M. , Riemann T. , Beaumont B. , Gibart P. 
Published: June 2006

AbstractEpitaxial Lateral Overgrowth (ELO) has proven to be an efficient technology to significantly decrease the density of extended defects in the 107 cm–2 ranges. In the present work, called the two‐step‐ELO (2S‐ELO) process, only the coalescence boundaries are defective. In addition in this 2S‐ELO modification, the tilt angle between the two laterally overgrowing wings was found to be negligible. The thickness dependence of the crystal quality of an ELO GaN/sapphire was investigated using a 50 × 0.5 µm X‐ray focused beam of the ESRF synchrotron storage ring. Micro diffraction allows following the mechanism of reduction of the density of extended defects. It is evidenced that no tilt occurs during the 2S‐ELO process. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Epitaxial growth and characterization of InN nanorods and compact layers on silicon substrates
Authors: Sánchez‐García M. A. , Grandal J. , Calleja E. , Lazic S. , Calleja J. M. , Trampert A. 
Published: June 2006

AbstractThis work reports on the morphology and optical properties of wurtzite InN layers grown by plasma assisted molecular beam epitaxy (PA‐MBE) on Si(111) substrates. The layer morphology can be controlled by the effective indium to nitrogen molecular flux ratio, from N‐rich conditions that lead to InN nanorods, to stoichiometric conditions leading to compact InN layers. The nanorods deliver a much higher intensity of the photoluminescence emission than compact layers, with a full width at half maximum down to 34 meV, indicative of a high crystal quality. Raman and X‐ray measurements on the InN nanorods and compact layers confirm the practical full relaxation of both types of materials. TEM measurements reveal a perfect epitaxial alignment of Si substrate‐AlN buffer and InN epilayer with clean AlN‐InN interfaces when growth conditions are optimized. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photoemission and X‐ray absorption studies of the electronic structure of GaN‐based diluted magnetic semiconductors
Authors: Hwang J. I. , Ishida Y. , Kobayashi M. , Osafune Y. , Mizokawa T. , Fujimori A. , Takeda Y. , Terai K. , Fujimori S‐I. , Saitoh Y. , Muramatsu Y. , Tanaka A. , Kondo T. , Munekata H. , Hashimoto M. , Tanaka H. , Hasegawa S. , Asahi H. 
Published: June 2006

AbstractWe have investigated the electronic structure of Cr‐ and Mn‐doped GaN using photoemission spectroscopy (PES) and X‐ray absorption spectroscopy (XAS). Cr and Mn XAS at the L‐edge have indicated that the Cr and Mn ions are in the tetrahedral crystal field and that their valences are trivalent and divalent, respectively. Upon Cr and Mn doping into GaN, new states were found to form in the band‐gap region of GaN. Resonant photoemission spectroscopy (RPES) has revealed that the main structure of the Cr 3d partial density of states (PDOS) appears within the band gap of GaN while that of the Mn 3d PDOS appears within the valence band of GaN and as a shoulder above the valence‐band maximum of GaN, indicating that the character of the doping‐induced states is different between Ga1–xCrxN and Ga1–xMnxN. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Meta‐GGA calculation of the electronic structure of group III–V nitrides
Authors: Litimein F. , Bouhafs B. , Nouet G. , Ruterana P. 
Published: June 2006

AbstractThe ground state electronic structure of wurtzite AlN, GaN, and InN has been calculated using full‐relativistic all‐electron full‐potential linearized‐augmented plane‐wave method. Several DFT exchange‐correlation functionals, including the recently proposed non‐empirical meta‐generalised gradient approximation (Meta‐GGA) have been used. The role played by relativistic effects and meta‐GGA functional on the band structures and the density of states is discussed. We find that the meta‐GGA improves the accuracy of the structural properties as well as the energies of the semicore d states in both GaN and InN. This new functional slightly outperforms the local density approximation (LDA) and the generalized gradient approximation (GGA) overall as to lattice parameters, bulk modulus, and valence band widths. We find also that the meta‐GGA induced modifications of the band structure are significant, but limited to the valence band states, while leaving all other features identical to LDA and GGA calculations. Finally, our results show that GaN and InN present anomalous dependence of the valence band splitting versus pressure. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
MOVPE growth of InAsN films on GaAs(001) substrates with an InAs buffer layer
Authors: Kuboya S. , Nakajima F. , Katayama R. , Onabe K. 
Published: June 2006

AbstractInAsN films of N content up to 3.5% without phase separation were grown on GaAs(001) substrates with a 1.9 μm‐thick InAs buffer layer by metalorganic vapor phase epitaxy (MOVPE). In order to grow the InAsN films with a high N content at low temperature that assures a non‐equilibrium growth environment, 1,1‐dimetylhydrazine (DMHy) and tertiarybutylarsine (TBAs), which can be efficiently decomposed at low temperatures, were adopted as the N and As precursors, respectively. The electron concentration evaluated by the Hall measurement increased with increasing N content and the electrons were degenerated, while the fundamental absorption edge which was determined by the FT‐IR absorption spectroscopy showed a blue‐shift with increasing N content. These results indicate that the Burstein–Moss effect (or band filling effect) is dominant over the bandgap reduction expected from the bandgap bowing. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
RF‐MBE growth and structural characterization of cubic InN films on GaAs
Authors: Nakamura T. , Iida K. , Katayama R. , Yamamoto T. , Onabe K. 
Published: June 2006

Abstractc‐InN (zincblende structure) films have been successfully grown on GaAs(001) substrates by rf‐plasma‐assisted molecular beam epitaxy. The X‐ray diffraction analysis has confirmed the growth of c‐InN films whose growth temperature was 400–550 °C. The structural properties (i.e. surface flatness and crystal quality) of the InN films are obviously improved for the growth condition of the near surface‐stoichiometry at the In‐rich side. By high resolution transmission electron microscopy images and 2θ/ω X‐ray reciprocal space mapping measurements, hexagonal‐phase InN (h‐InN) is found to be generated from c‐InN{111} facets. The volume content of c‐InN is estimated to be ∼82% at maximum based on an analysis of the X‐ray diffraction intensity. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Assessment of phonon mode characteristics via infrared spectroscopic ellipsometry on a‐plane GaN
Authors: Darakchieva V. , Paskova T. , Paskov P. P. , Arwin H. , Schubert M. , Monemar B. , Figge S. , Hommel D. , Haskell B. A. , Fini P. T. , Nakamura S. 
Published: June 2006

AbstractGeneralized infrared spectroscopic ellipsometry was applied to study the vibrational properties of anisotropically strained a‐plane GaN films with different thicknesses. We have established a correlation between the phonon mode parameters and the strain, which allows the determination of the deformation potentials and strain‐free frequency of the GaN A1(TO) mode. These results are compared with previous theoretical and experimental findings and discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Micro‐photoluminescence studies of InGaN/GaN quantum dots up to 150 K
Authors: Sebald K. , Lohmeyer H. , Gutowski J. , Yamaguchi T. , Hommel D. 
Published: June 2006

AbstractWe present photoluminescence measurements on single InGaN quantum dots grown by metalorganic vapor phase epitaxy. The spatially and spectrally resolved luminescence properties of the single quantum dots were measured using low‐temperature micro‐photoluminescence spectroscopy. The observed sharp emission lines of the quantum dots were characterized by excitation density dependent measurements. They can easily be observed at temperatures up to 150 K. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analytical model for the quantum‐confined Stark effect including electric field screening by non‐equilibrium carriers
Authors: Bulashevich K. A. , Karpov S. Yu. , Suris R. A. 
Published: June 2006

AbstractWe have derived an analytical approximation for the energy levels in a symmetric quantum well applicable in a wide range of the electric field variation. Suppression of the quantum‐confined Stark effect due to the electric field screening by non‐equilibrium carriers is considered self‐consistently within the perturbation theory. Theoretical predictions are compared with available observations. Specific features of the quantum‐confined Stark effect in light‐emitting diode heterostructures are discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
N‐plasma assisted MBE grown GaN films on Si(111)
Authors: Gangopadhyay Subhashis , Schmidt Thomas , Falta Jens 
Published: June 2006

AbstractGaN films were grown by rf‐plasma assisted molecular beam epitaxy on nitrified Si(111) surfaces. Scanning tunneling microscopy (STM), low energy electron diffraction (LEED), and X‐ray photoelectron spectroscopy (XPS) have been used to characterize the structural and chemical properties of the GaN films. The XPS results show that GaN growth can be initiated only at temperatures below 650 °C. LEED indicates an improvement of the crystalline quality after introduction of a crystalline Si3N4 interface layer. This is confirmed by STM, where an atomically resolved 3 × 3 reconstruction for thin GaN films is observed as well as a smooth growth morphology. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mapping misorientation and crystallographic tilt in GaN layers via polychromatic microdiffraction
Authors: Barabash R. I. , Ice G. E. , Liu W. , Roder C. , Figge S. , Einfeldt S. , Hommel D. , Katona T. M. , Speck J. S. , DenBaars S. P. , Davis R. F. 
Published: June 2006

AbstractThe spatial distribution of strain, dislocations, and crystallographic orientation in uncoalesced and coalesced GaN layers grown on striped Si or SiC substrates was studied by polychromatic X‐ray microdiffraction and high resolution monochromatic X‐ray diffraction. Tilt boundaries formed at the column/wing interface depending on the growth conditions and geometry of the striped substrate. The measurements revealed that the free‐hanging wings are tilted upward at room temperature. A misorientation between the GaN(0001) and the Si(111) or SiC(0001) surface normal is observed. Distinct structural properties of the pendeo and cantilever epitaxially grown samples are discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Unintentionally doped InN grown onto an atomically flat AlN intermediate layer using plasma‐assisted molecular beam epitaxy
Authors: Wang K. R. , Tu L. W. , Lin S. J. , Chen Y. L. , Jiang Z. W. , Chen M. , Hsiao C. L. , Cheng K. H. , Yeh J. W. , Chen S. K. 
Published: June 2006

AbstractUnintentionally doped InN has been grown onto an atomically flat AlN intermediate layer on top of the Si(111) substrate using plasma‐assisted molecular beam epitaxy (PA‐MBE). Though there are lots of micrometer‐size indium droplets randomly distributed on the top of the surface, the highest electron mobility of this InN thin film measured at room temperature by van der Pauw method is still higher than 1000 cm2/V s with a carrier concentration of 5–8.9 × 1018 cm–3. A symmetrical X‐ray rocking curve is measured and the full‐width‐at‐half‐maximum (FWHM) of this sample is 1089 arcsec. In the meantime, the threading dislocation (TD) density of this material is estimated to around 9.8 × 108 cm–2 – 7.5 × 109 cm–2 depending on the probing regions that are studied by the etching technique and field‐emission scanning electron microscopy (FE‐SEM). (2 × 1) in situ reflection high‐energy electron diffraction (RHEED) patterns show that this sample is grown under In‐rich environment with possible In‐terminated surface. From the FE‐SEM pictures which were taken from the samples after 10 minutes etching in hydrochloride, the surface morphology shows In‐polarity‐like patterns that coincide with those procured in RHEED. To select and grow a high‐quality laminated AlN as intermediate layer is believed to be the major step in obtaining this high electron mobility InN thin film on Si substrate. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
N‐polarity GaN on sapphire substrate grown by MOVPE
Authors: Matsuoka Takashi , Kobayashi Yasuyuki , Takahata Hiroko , Mitate Toshitugu , Mizuno Seiichiro , Sasaki Atsushi , Yoshimoto Mamoru , Ohnishi Tuyoshi , Sumiya Masatomo 
Published: June 2006

AbstractN‐polar GaN was grown on (0001) sapphire using two‐step growth technique by MOVPE. In the growth, the key points were the controlling of the density of nuclei in a buffer layer and promoting lateral growth at high temperature. The grown GaN films had mirror‐like smooth surfaces and were proved to have N‐polarity using convergent‐beam electron diffraction and coaxial impact‐collision ion spectroscopy. The FWHM of this GaN in the ω‐scan was also much narrower than the previous reports. The density of threading dislocations was much less than for usual Ga‐polar GaN grown with a GaN or AlN buffer layer by MOVPE and MBE. In PL at room temperature, the strong edge emission was observed as Ga‐polarity. The p‐type conduction in Mg‐doped GaN was also realized by the same methods as for Ga‐polarity. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigating the electrical properties of Si donors in AlxGa1–xN alloys
Authors: James G. R. , Omnès F. , Leitch A. W. R. 
Published: June 2006

AbstractIn this paper a study of the electrical properties of Si‐doped AlxGa1–xN is presented. The AlxGa1–xN layers, grown using the metalorganic chemical vapour deposition technique, were studied using variable temperature Hall effect and persistent photoconductivity measurements. High quality conducting AlxGa1–xN layers were obtained for 0 ≤ x ≤ 0.5, with the mobility decreasing from 215 cm2/V s (GaN) to 10 cm2/V s (Al0.51Ga0.49N), at 300 K. The carrier concentration of these layers was typically between 2.5 × 1018 cm–3 and 7 × 1017 cm–3 at 300 K. For AlxGa1–xN layers with 0 ≤ x ≤ 0.41 the temperature dependence of the carrier concentration between 300 and 15 K could be studied, yielding the Si donor activation energy. The carrier concentrations of higher Al content samples (0.5 ≤ x ≤ 0.65) could not be accurately measured below 300 K, and thus the Si activation energy was obtained from the temperature dependence of the resistivity. It was found that the Si activation energy escalated with increasing Al content of the layers, and followed the trend predicted for a shallow hydrogen‐like donor, up to x = 0.65. Illumination of the samples at low temperature with a blue LED showed that the layers exhibit little persistent photoconductivity, further confirmation that Si remains a shallow donor in AlxGa1–xN. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Site selectivity of Fe3+Gaand the formation of Fe3+Ga–Gaipairs in GaN
Authors: Gehlhoff W. , Azamat D. , Hoffmann A. 
Published: June 2006

AbstractThe electron paramagnetic resonance (EPR) spectra of Fe‐related defects in high quality thick freestanding hydride vapor phase (HVPE) grown GaN have been studied in the X‐ and Q‐band. The dominating part of the complex resonance pattern is due to isolated Fe3+(3d5,S= 5/2) on the two equivalent Ga sites A and B with C3Vpoint symmetry in the hexagonal GaN unit cell. These two physically equivalent sites, caused by the ABAB stacking sequence of the wurtzite structure, can be distinguished by EPR for electron spin systemsS≥ 2. We found a preferential incorporation of Fe in one of the two types of Ga sites. Moreover, despite the strong overlap with the intensive Fe3+transitions we could identify the main part of the additional observed very weak lines asERRORpairs. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Identification of catecholamines in the immune system by desorption/ionization on silicon
Authors: Kraj Agnieszka , Jarzebinska Justyna , Gorecka‐Drzazga Anna , Dziuban Jan , Silberring Jerzy 
Published: June 2006

AbstractDesorption/ionization from porous silicon dioxide (DIOSD), in combination with a standard matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) instrument, was used for the identification of catecholamines in the human peripheral blood lymphocytes. A routine MALDI‐TOF analysis does not allow for sensitive detection of low molecular mass compounds (i.e. below 400 Da) due to the pronounced background ions arising from the matrix. Therefore, we have tested DIOSD methodology for the identification of catecholamines in the immune system. Using DIOSD, catecholamines were unambiguously identified in the cell extract of peripheral blood lymphocytes at the femtomolar level. The DIOSD extends the possible use of MALDI‐TOF mass spectrometry towards small molecules that were previously detected by other methods. Copyright © 2006 John Wiley & Sons, Ltd.
Mass spectrometry techniques for detection of ligand‐dependent changes in the conformational flexibility of cellular retinol‐binding protein type I localized by hydrogen/deuterium exchange
Authors: Careri M. , Elviri L. , Mangia A. , Zagnoni I. , Torta F. , Cavazzini D. , Rossi G. L. 
Published: June 2006

AbstractHydrogen/deuterium exchange, measured by electrospray ionization with orthogonal quadrupole time‐of‐flight mass spectrometry (ESI‐Q‐TOFMS) and by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS), was used as a means to probe and map differences in conformational flexibility between the ligand‐free and ligand‐bound forms of cellular retinol‐binding protein type I. Labelled fragments were obtained by digestion of the protein with pepsin. The differences in space‐resolved time courses of deuterium incorporation identified regions that exhibit a remarkably higher degree of flexibility in the apo‐protein than in the holo‐protein. These segments encompass residues that are thought, on the basis of structural homology of the retinol carrier with other members of the intracellular lipid‐binding proteins family, to belong to the dynamic portal through which all‐trans retinol can access its high‐affinity, solvent‐shielded, binding site. Copyright © 2006 John Wiley & Sons, Ltd.
The complexation of two different ammonium ions with resorcarenes in protic solvent medium investigated by electrospray ionisation Fourier transform ion cyclotron resonance mass spectrometry
Authors: Mäkinen Marko , Karjalainen Antti , Vainiotalo Pirjo 
Published: June 2006

AbstractThe complexations of two ammonium ions (guests) with two resorcarenes (hosts) were investigated using electrospray ionisation Fourier transform ion cyclotron resonance mass spectrometry. Although the two guests and the two hosts were noticeably similar, the quantity of the corresponding supramolecular complexes formed varied significantly due to the differences in host conformations and guest ability to form non‐covalent interactions. Copyright © 2006 John Wiley & Sons, Ltd.
Simultaneous identification and verification of Bacillus anthracis
Authors: Krishnamurthy Thaiya , Hewel Johannes , Bonzagni Neil J. , Dabbs Jason , Bull Robert L. , Yates John R. 
Published: June 2006

AbstractSpecific identification of Bacillus anthracis (B. anthracis) is vital for the accurate treatment of afflicted personnel during biological warfare situations and civilian terrorist attacks. In order to accomplish this, we have subjected the lysates from B. anthracis to affinity purification using monoclonal antibodies for the selected antigenic protein present in the bacteria. The bound antigenic protein was identified by multi‐dimensional protein identification technology (MudPIT) to be a surface layer protein EA1. The same antigen was identified from the lysates from a few strains of B. anthracis demonstrating the observation to be common for B. anthracis strains. Hence, this presents an effective pathway for the identification of the bacteria present in unknown samples of various origins. Generation of a database containing the EA1 protein has been found to be useful in the database search of unknown samples. Published in 2006 by John Wiley & Sons, Ltd.
The effects of in situ chemical oxidation on microbiological processes: A review
Authors: Sahl Jason , Munakata‐Marr Junko 
Published: June 2006

AbstractThe effects of in situ chemical oxidation (ISCO) on biological processes, as reported in the literature, were researched to determine if coupling ISCO with in situ bioremediation could be achieved in field and laboratory experiments. Literature was compiled concerning the effect of ISCO on microbial communities following addition of a chemical oxidant at a range of concentrations designed to treat a variety of subsurface contaminants. The results indicate that although microbial communities may potentially be adversely affected by chemical oxidation in the short term, a rebound of microbial biomass and/or bioremediation activity can be expected. Successfully coupling ISCO with bioremediation in field applications may be a cost‐effective method of achieving risk‐based site remediation goals. © 2006 Wiley Periodicals, Inc.