bluuebunny/crossref_metadata_2025_split huggingface dataset:
Wear‐out and breakdown of thermally grown Ta2O5 insulating films on plasma oxynitrided Si substrates
Authors: Novkovski N. , Atanassova E. 
Published: June 2006

AbstractWear‐out and breakdown at constant current stress (J = 10 mA/cm2) were studied for Ta2O5 insulating layers (30 nm thick) thermally grown over plasma oxynitrided (5 to 15 s at room temperature) Si substrates. For injected charges Qinj lower than 100 C/cm2 hard breakdown occurs, while for Qinj higher than 100 C/cm2 it appears that only progressive breakdowns are possible. An optimum of the dielectric properties was found for oxynitridation times as long as 10 s, simultaneously for the hard breakdown charge (33 C/cm2 on a capacitors with an area of 2.5 × 10–3 cm2), the equivalent thickness (8.24 nm) and the wear‐out (variation of the gate voltage smaller than 50 mV, during the stress up to 100 C/cm2). The observed optimum was attributed to a defect free relaxed interfacial structure containing approximately 1 × 1014 cm–2 nitrogen atoms in the first atomic monolayer adjacent to the Si substrate, as one with a significant improvement of the SiOxNy interfacial layer relative permittivity (5.5) without considerable reduction of the tunneling barrier heights. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of an external mechanical strain on the character of the magneto‐electric effect in epitaxial films of yttrium iron garnet
Authors: Koronovskyy V. E. 
Published: June 2006

AbstractEpitaxial films of yttrium iron garnet (YIG) exhibit electric‐field‐dependent magnetic properties that have been experimentally measured as a function of the applied magnetic field and as a function of strain. The laser polarimeter technique was used for researching the magneto‐electric manifestation – the electromagneto‐optical (EMO) effect. Magnetic‐field dependencies, the acquired EMO effect, testify to an influence of an external mechanical strain not only on the value of the EMO effect, but also on the character of the EMO manifestation in YIG films. These magneto‐electric properties are discussed on the basis of the model of lowering of symmetry in the crystal due to nonuniform deformations of the YIG film. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Prediction of intragranular strains in metallic polycrystals with a two‐level homogenisation approach: Influence of dislocation microstructure on the mechanical behaviour
Authors: Gloaguen D. , François M. 
Published: June 2006

AbstractA two‐level homogenisation approach is applied to the micro‐mechanical modelling of the elasto‐plasticity of polycrystalline materials during various strain‐path changes. The model is tested by simulating the development of intragranular strains during different complex loads. Mechanical tests measurements are used as a reference in order to validate the model. The anisotropy of plastic deformation in relation to the evolution of the dislocation structure is analysed. The results demonstrate the relevance of this approach for FCC polycrystals. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of Ba on ferroelectric and piezoelectric properties of the PLZT (1.2/55/45) system
Authors: Koduri Ramam , Hermosilla Luis Salinas 
Published: June 2006

AbstractFerroelectric Pb0.982–zLa0.012Δ0.006Baz(Zr0.55Ti0.45)O3 (PLZT; z = 0–6 mol%) ceramic compositions were fabricated by a mixed‐oxide method. X‐ray diffraction studies of sintered ceramics indicate the coexistence of rhombohedral and tetragonal phases in the 5 mol% Ba‐doped PLZT composition. Grain growth is inhibited with increasing Ba concentration in the PLZT system as evidenced by scanning electron micrographs. Dielectric constant and dielectric loss as a function of temperature suggest that ϵrt and tan δ are increased up to compositions containing 4 and 5 mol% Ba, respectively. The dielectric maximum (ϵTc) decreased to 4 mol% Ba and gradually increased to 6 mol% Ba, whereas, with increasing Ba concentration in the PLZT system, the Curie temperature (TC) decreased from the composition with no Ba to that with 6 mol% Ba. Relaxor behavior as a function of temperature and frequency was studied over the composition series. As the Ba concentration increased, the coercive field (Ec) showed a gradual enhancement. Remanent (Pr) and spontaneous (Ps) polarizations decreased to the 5 mol% Ba composition. Piezoelectric charge coefficient (d33), piezoelectric planar coupling coefficient (kp) and piezoelectric thickness coupling coefficient (kt) increased to the 4 mol% Ba composition, which are potential compositions for sensor and actuator applications. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Single‐crystal nanorings of β‐gallium oxide synthesized using a microwave plasma
Authors: Zhu F. , Yang Z. X. , Zhou W. M. , Zhang Y. F. 
Published: June 2006

AbstractIn this study, a new method for synthesizing single‐crystal ring‐like β‐Ga2O3 nanobelts (here named nanorings), of only 0.2–1 µm in diameter, is presented. A microwave plasma method involving liquid‐phase gallium containing H2O in an Ar atmosphere, using silicon as the substrate, is used for the first time. The morphology and structure of the nanorings were analysed using scanning electron microscopy and X‐ray diffraction. The morphology of β‐Ga2O3 nanobelts was also characterized using transmission electron microscopy (TEM) and high‐resolution TEM in order to propose possible growth mechanisms of the β‐Ga2O3 nanorings. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
p‐type transparent conducting oxides
Authors: Sheng Su , Fang Guojia , Li Chun , Xu Sheng , Zhao Xingzhong 
Published: June 2006

AbstractThe recent advance of p‐type transparent conductive oxide thin films is reviewed. The focus is on p‐type transparent oxide semiconductors CuAlO2, CuGaO2, CuInO2, SrCu2O2, and LaCuOCh (Ch = chalcogen). These materials and related device applications are then shown as examples. Room temperature operation of current injection emission from ultraviolet light‐emitting diodes based on p‐SCO/n‐ZnO p–n junctions has been demonstrated. This changed with the discovery of p‐type transparent conducting oxides, thereby opening up the possibility for all‐oxide transparent electronics. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of strain in the reduction of the internal electric field in GaN/AlN quantum dots grown on a‐plane 6H‐SiC
Authors: Cros A. , Budagosky J. A. , García‐Cristóbal A. , Garro N. , Cantarero A. , Founta S. , Mariette H. , Daudin B. 
Published: June 2006

AbstractThe strain state of stacks of GaN/AlN quantum dots (QDs) grown on (0001) and (11$ \bar 2 $0) 6H‐SiC has been investigated by means of Raman spectroscopy. Depending on the orientation of the wurtzite axis with respect to the growth direction it is found that the piezoelectric contribution to the electrostatic potential may either reinforce that arising from the spontaneous polarization or oppose it. The experimental results are compared with a theoretical model for the strain and polarization field in QDs of both orientations that allows the calculation of the electrostatic potential in the QDs. Both the experimental results and the theoretical model indicate that the internal electric field and electrostatic potential are strongly reduced in the QDs grown on (11$ \bar 2 $0) 6H‐SiC as compared to those grown along the wurtzite c‐axis. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Degenerate four‐wave mixing spectroscopy of GaN films on various substrates
Authors: Ishiguro T. , Toda Y. , Adachi S. , Mukai T. , Hoshino K. , Arakawa Y. 
Published: June 2006

AbstractWe have carried out time‐integrated and spectrally‐resolved four‐wave mixing (FWM) measurements to study the effects of built‐in strain within GaN films on their exciton structures and on their coherent dynamics. Precise values for exciton energies, linewidths, and oscillation periods of quantum beats were presented. Remarkable phase shifts of the quantum beats were observed in the GaN films on a‐sapphire, suggesting the exciton–exciton interaction caused by the reduction of the crystal symmetry. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Study of InAsN quantum dots on GaAs substrates by molecular beam epitaxy
Authors: Ueta A. , Akahane K. , Gozu S. , Yamamoto N. , Ohtani N. 
Published: June 2006

AbstractInAsN QDs on (001) GaAs substrates were studied. Each InAsN QD was surrounded by four {011} facets and had a pyramidal shape. However, InAs QDs had a half sphere shape. The InAsN QDs had size distributions with two maxima. This might be explained by the existence of very stable {011} facets and curved surfaces between the {011} facets. The curved surfaces act as the incorporation sites to grow the QD larger. This means that large InAsN QDs will be suppress the further growth, because of the smaller occupations of the curved surfaces to the total surface area of the InAsN QD. Excess In atoms supplied on the {001} plane will accumulate strains and form new small QDs by the Stranski–Krastanow (S–K) growth mode. This turns out two maxima of the size distribution. These results will open the possibility of obtaining the size control and small distributions of the InAsN QDs. We investigated the emission properties of these InAsN QDs. An emission peak of nearly 1300 nm from the InAsN QDs with a plasma power of 350 W was observed. InAsN QDs are an attractive material for achieving emissions in the fiber‐optic communication wavelengths. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Raman study of N bonding in AlGaAs/InGaAsN multiquantum wells
Authors: Lazić S. , Calleja J. M. , Hey R. , Ploog K. 
Published: June 2006

AbstractWe report resonant Raman scattering measurements on InGaAsN/AlGaAs multiquantum wells grown by plasma‐assisted molecular beam epitaxy. Sharp vibration modes have been observed at 323, 402, 454 and 501 cm–1. They are resonant in the energy range 1.81–1.87 eV at decreasing energies for increasing N concentration. The resonance energies reveal the influence of the N concentration on the barrier gap at the multiquantum well interfaces. The peaks are interpreted in terms of local vibrations involving GaN and AlN units and pairs. They seem to form mostly at the quantum well interfaces due to preferential N bonding to Al. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The performance of AlGaN solar blind UV photodetectors: responsivity and decay time
Authors: Cherkashinin G. , Lebedev V. , Wagner R. , Cimalla I. , Ambacher O. 
Published: June 2006

AbstractThe responsivity and the decay time of AlGaN solar blind UV‐detectors have been studied. The photodetectors have shown a good spectral responsivity in a narrow spectral range (220 < λ < 300 nm) and a short time response with the best estimated characteristic time constant of τ ∼ 30 ms measured at room temperature. Possible mechanisms responsible for the persistent photoconductivity (PPC) effect in AlxGa1–xN (x = 0.51) are analyzed. A shape of the spectral response as a function of the applied voltage is analyzed in the frameworks of the space‐charge limited current model. It has been shown that the main source of PPC is traps above the Fermi level. PPC occurs when the density of free carriers equals the density of the traps. The model attributing PPC to the spatial separation of the photoexcited electrons and holes by the macroscopic potential barrier is not supported by our photocurrent studies. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Doping of GaN with Fe and Mg for spintronics applications
Authors: Bonanni Alberta , Simbrunner Clemens , Wegscheider Matthias , Przybylinska Hanka , Wolos Agnieszka , Sitter Helmut , Jantsch Wolfgang 
Published: June 2006

AbstractMetal‐organic chemical vapour deposition of GaN:Fe and (Ga, Fe)N:Mg has been carried out in order to optimize the growth process and to investigate the effectiveness of Fe ions and Mg acceptors incorporation. All samples have been investigated via high‐resolution X‐ray diffraction, secondary‐ion mass spectroscopy, electron paramagnetic resonance (EPR) and magnetization measurements. Co‐doping of Fe and δ‐Mg has been found to promote the acceptors incorporation and EPR data, supported by superconducting quantum interference device magnetometry experiments, reveal the presence of Fe ions in two charge states, namely the Fe3+ responsible for Curie paramagnetism and the Fe2+ tentatively correlated to van Vleck paramagnetism. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Strong light–matter coupling in GaN microcavities grown on silicon(111) at room temperature
Authors: Sellers I. R. , Semond F. , Leroux M. , Massies J. , Henneghien A‐L. , Disseix P. , Leymarie J. , Vasson A. 
Published: June 2006

AbstractWe present experimental results demonstrating strong light–matter coupling at room temperature in bulk GaN microcavities grown on silicon(111). Simple low finesse planar microcavities show a Rabi energy as high as 60 meV at room temperature. We also demonstrate room temperature strong‐coupling from a bulk GaN microcavity with epitaxial distributive Bragg reflectors (DBRs). Furthermore, for this structure at low temperature, the strong coupling of both the A and B excitonic features of GaN with the cavity mode are clearly resolved for the first time in such a microcavity. At room temperature a Rabi energy of 50 meV is observed, and well reproduced using numerical analysis describing the interaction of both the A and B excitonic states with the photonic mode. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Localized donor state above the conduction band minimum in InN revealed by high pressure and temperature transport experiments
Authors: Dmowski L. H. , Dybko K. , Plesiewicz J. , Suski T. , Lu H. , Schaff W. , Kurouchi M. , Nanishi Y. , Konczewicz L. , Cimalla V. , Ambacher O. 
Published: June 2006

AbstractWe have studied the pressure and temperature dependences of Hall electron concentration and mobility in degenerated, not intentionally doped InN samples. The results obtained for a whole set of samples with electron concentrations from 5.4 × 1017 cm–3 to 3.3 × 1018 cm–3 consistently revealed the existence of a localized donor type state resonant with the conduction band. The concentration of this state is of the same order in all studied samples and not exceeds 1018 cm–3. Population of this state determines electrical properties of InN samples with low carrier concentration. This donor state is not the main source of conducting electrons in these not intentionally doped samples and can be entirely populated and hidden in samples with high electron concentration exceeding about 3 × 1018 cm–3. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical polarization anisotropy in strained A‐plane GaN films on R‐plane sapphire
Authors: Ghosh Sandip , Misra Pranob , Grahn Holger T. , Imer Bilge , Nakamura Shuji , DenBaars Steven P. , Speck James S. 
Published: June 2006

AbstractWe have used polarized photoreflectance (PR) spectroscopy to study [11$ \bar 2 $0]‐oriented A‐plane GaN films on R‐plane sapphire substrates. For this type of films, the c‐axis of GaN lies in the film plane. When the probe beam is polarized perpendicular to the c‐axis, we observe a single feature in the PR spectrum, while two features at higher energies are observed for parallel polarization. Comparing the transition energies with the ones obtained by electronic band‐structure calculations, we identify the observed PR spectral features as the three possible transitions around the fundamental band gap of GaN. However in comparison to unstrained GaN, their polarization properties and energies have been significantly modified by the in‐plane anisotropic strain in the film. Finally, we can also determine the individual in‐plane anisotropic strain components. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Four‐wave mixing measurements of biexcitons in uniaxially‐strained GaN films
Authors: Adachi Satoru , Toda Yasunori , Ishiguro Tetsuro 
Published: June 2006

AbstractBiexcitons of GaN under uniaxial strain have been investigated by spectrally‐resolved four‐wave mixing (FWM) technique. Two kinds of biexcitons were observed clearly and the binding energies were obtained. Since the uniaxial strain changes the exciton structure, the biexciton binding is modified and biexciton has also fine structure, which was revealed in the FWM spectra that were obtained by rotating the linearly polarized excitation against the direction of uniaxial strain. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Pressure and composition dependence of the electron effective mass in GaAs1–xNx
Authors: Gorczyca I. , Christensen N. E. , Svane A. 
Published: June 2006

AbstractThe electronic band structures of GaAs1–xNx alloys are calculated ab initio using a supercell approach in connection with the full‐potential linear muffin‐tin‐orbital method. Alloying GaAs with small amounts of GaN modifies substantially the conduction bands. The lowest conduction band exhibits a strong nonparabolicity, which is reflected in the dependence of the electron effective mass on the k‐vector. The calculations indicate that for x above 0.01 the alloys have electron effective masses, which are significantly larger than that of pure GaAs. In addition, the effective mass decreases with x. Hydrostatic pressure is found to strongly influence the electron effective masses. The pressure coefficient of the mass at the conduction band minimum varies non‐linearly with x. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Reflectance and photoluminescence studies of InGaN/GaN multiple‐quantum‐well structures embedded in an asymmetric microcavity
Authors: Lin D. Y. , Shiu J. J. , Lin C. F. 
Published: June 2006

AbstractUsing reflectance (R) and photoluminescence (PL) measurements InGaN/GaN multiple‐quantum‐well (MQW) structures embedded in an asymmetric microcavity with different thickness of stacking pairs have been studied. The asymmetric microcavity structures are composed of a cavity sandwitched between the air/semiconductor interface and a mirror using distributed Bragg reflector (DBR). For the DBR with thinner AlN layers the high‐reflectivity stop band locates at higher photon energy. The luminescence efficiency and the spectrum of InGaN/GaN multiple‐quantum‐well structures will be modified by the microcavity. A comparison of PL with R spectra shows that the emission efficiency can be enhanced by matching up the luminescence spectrum coming from the MQW and the high‐reflectivity stop band. From the blue shift of the cavity modes as a function of incident angles the refractive index and cavity length can be determined. By measuring the PL spectra as a function of emission angle, it is found that the PL spectra were predominatly determined by microcavity resonances. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Resonant Raman scattering in InGaN alloys
Authors: Davydov V. Yu. , Klochikhin A. A. , Goncharuk I. N. , Smirnov A. N. , Sakharov A. V. , Skvortsov A. P. , Yagovkina M. A. , Lebedev V. M. , Lu Hai , Schaff William J. 
Published: June 2006

AbstractA strong resonant behavior of the Raman scattering from LO‐phonons in n‐InGaN alloys at excitation near the interband absorption threshold was observed. An approach has been developed to describe the resonant Raman cross sectional profile in the presence of a Burstein‐Moss shift of the interband optical transitions. It has been shown that a simultaneous study of absorption, photoluminescence, and Raman spectra provides reliable information about the band gap and can be efficient for the alloy characteriza‐tion. Our data show that the band gap composition dependence of InGaN is characterized by the strongly nonlinear behavior with the large bowing parameter of 2.5–2.6 eV. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electric fields in AlGaN/GaN quantum well structures
Authors: McAleese C. , Costa P. M. F. J. , Graham D. M. , Xiu H. , Barnard J. S. , Kappers M. J. , Dawson P. , Godfrey M. J. , Humphreys C. J. 
Published: June 2006

AbstractThis paper presents a comparative study of the magnitude of the electric fields in AlGaN/GaN quantum well structures, measured using electron holography in a transmission electron microscope and estimated from a comparison of low temperature photoluminescence peak energies with calculated values. The values derived from the two techniques were found to be in reasonable agreement for the structures examined here. A larger field across the GaN well was observed from a single quantum well compared to a 10 period structure with equivalent well thickness, while the presence of an electric field across the barrier of the single quantum well was also detected by electron holography. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth and optical characterization of InAsN quantum dots
Authors: Tsurusawa H. , Nishikawa A. , Katayama R. , Onabe K. 
Published: June 2006

AbstractSelf‐assembled InAsN quantum dots (QDs) have been grown by rf‐plasma‐assisted molecular beam epitaxy (RF‐MBE) on GaAs(001) substrates via a 2‐monolayer (ML)‐thick InAs wetting layer. The InAsN QDs are typically 30–70 nm in diameter and 3–7 nm in height. The dot density was 3.6 × 109–2.3 × 1010 cm–2 for the fluxes corresponding to the nominal thicknesses of 3.0–4.0 MLs. As the nominal thickness increases, the dot density increases, while the diameter decreases. The low‐temperature (10 K) photoluminescence (PL) of the QD samples shows emission spectra in the wavelength range of 1.2–1.6 μm apparently caused by the N incorporation (0.8–2.0%) into the QDs. The QD size distribution causes broad emission spectra. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
X‐ray absorption near edge spectroscopy at the Mn K‐edge in highly homogeneous GaMnN diluted magnetic semiconductors
Authors: Sancho‐Juan O. , Cantarero A. , Martínez‐Criado G. , Olguín D. , Garro N. , Cros A. , Salomé M. , Susini J. , Dhar S. , Ploog K. 
Published: June 2006

AbstractWe have studied by X‐ray absorption spectroscopy the local environment of Mn in highly homogeneous Ga1–xMnxN (0.06 < x < 0.14) thin epilayers grown by molecular beam epitaxy on [0001] SiC substrates. The measurements were performed in fluorescence mode around the Ga and Mn K‐edges. In this report, we focus our attention to the X‐ray absorption near edge spectroscopy (XANES) results. The comparison of the XANES spectra corresponding to the Ga and Mn edges indicates that Mn is substitutional to Ga in all samples studied. The XANES spectra measured at the Mn absorption edge shows in the near‐edge region a double peak and a shoulder below the absorption edge and the main absorption peak after the edge, separated around 15 eV above the pre‐edge structure. We have compared the position of the edge with that of MnO (Mn2+) and Mn2O3 (Mn3+). All samples studied present the same Mn oxidation state, 2+. In order to interprete the near‐edge structure, we have performed ab initio calculations with a 2 × 2 × 1 supercell (∼6% Mn) using the full potential linear augmented plane wave method as implemented in the Wien2k code. The calculations show the appearance of Mn anti‐bonding t2g bands, which are responsible for the pre‐edge absorption. The shoulder and main absorption peaks are due to transitions from the valence band 1s‐states of Mn to the p‐contributions of the conduction bands. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)