bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vectorial selective surface effects in the optical absorption and photoelectric emission of thin metal films
Authors: Meessen A. 
Published: March 2011

AbstractThe “surface effect” is expected to become observable in the photoelectric emission, and even more early in the optical absorption of very thin metal films. It corresponds to a modified Drude absorption where the electron mean free path is of the order of magnitude of the film thickness. But there is a strong “vector effect” in films with perfectly plane surfaces. The quantum mechanical calculation yields the same result as the modified classical Drude theory, with the additional prediction of a film‐thickness dependent absorption‐threshold. Other related surface effects are briefly discussed, and it is suggested that the excitation of surface plasmons may also lead to a “vectorial, selective photoelectric emission”.
Magnetoabsorptionsmessungen an Tellur
Authors: Grosse P. , Winzer K. 
Published: March 2011

AbstractIm Bereich der elektronischen Bandkante wurden an Tellur Absorptionsspektren hoher Auflösung für die beiden Hauptpolarisationsrichtungen gemessen. Der Einfluß von Magnetfeldern bis 32 kG auf diese Spektren wurde für die drei Orientierungen (E ⟂ c, B ⟂ c, B ‖ E), (E ‖ c, B ‖ c, B ‖ E) und (E ‖ c, B ⟂ c, B ⟂ E) untersucht. Exzitonen werden für beide Polarisationsrichtungen nachgewiesen. Die Extrapolation der Magnetoabsorptionsspektren auf B = 0 ergibt für beide Polarisationsrichtungen den gleichen Bandabstand von Eg = 0,335 eV bei 10°K. Aus den drei verschiedenen ausgewählten Magnetoabsorptionsspektren kann der Tensor für die Löcher‐ und Elektronenmassen getrennt angegeben werden, für den Landé‐Faktor nur der kombinierte. Die Löchermassen stimmen mit anderen Meßergebnissen überein. Die Elektronenmassen ergeben sehr kleine Werte.
The orientation distribution function of the crystallites in cold‐rolled and annealed low‐carbon steel sheets
Authors: Bunge H.‐J. 
Published: March 2011

AbstractThe three‐dimensional orientation distribution function of the crystallites in cold‐rolled end annealed low‐carbon steel sheets, which is not directly measurable, has been calculated from pole figures. It consists of a continuous row of orientations together with some ideal orientation components.
A contribution to the problem of the spatial distribution of the spontaneous magnetization in thin films
Authors: Valenta L. , Haubenreisser W. , Brodkorb W. 
Published: March 2011

AbstractThis report summarizes some of the calculations based on the Heisenberg model using the molecular field theory approximation and the Green's function technique. The results are compared with the corresponding ones of other authors. Some consequences are pointed out for the experiment e.g. application of the Mössbauer effect.
Dependence of the ferromagnetic domain width on the thickness of cobalt foils
Authors: Gemperle R. , Gemperle A. 
Published: March 2011

AbstractPrevious measurements of the dependence of the domain width on the crystal thickness of cobalt are extended down to a thickness of 400 Å by means of the Lorentz transmission electron microscopy. In crystals thinner than 4 μm the domain width is proportional to the square root of the thickness as expected for the simple plate domain structure (Kittel type) without surface domain structure. However, the experimental dependence is shifted slightly compared to the theoretical curve.
The ultrasound generation under the gunn effect in a piezoelectric material
Authors: Grinberg A. A. , Kastalskii A. A. 
Published: March 2011

AbstractA theoretical investigation is made of the possibility of obtaining ultrasound oscillations during the periodic rise and movement of high field domains in the case of the Gunn effect in piezoelectrics. It is shown that for definite correlations between the sound and drift velocity of a domain a resonant ultrasound amplification at frequencies being multiples of the frequency of the current oscillations may be observed. This effect is considered for GaAs.
Effect of temperature on the dielectric relaxation in polycrystalline ferrites
Authors: Haberey F. , Wijn H. P. J. 
Published: March 2011

AbstractThe dielectric constant and the conductivity of polycrystalline ferrites are measured at temperatures between 100 and 400°K and at various frequencies. Different activation energies are obtained for the d.c. and the h.f. conductivity of the samples. Both positive and negative temperature coefficients of the conductivity and the dielectric constant depending on frequency are observed. It is found that the temperature dependence of the dielectric constant is mainly due to the temperature dependence of the conductivities of both types of the Maxwell‐Wagner layers.
Spectres d'absorption et de réflexion, dans l'infrarouge lointain, de ZnSe, ZnTe et CdSe à basse température
Authors: Hadni A. , Claudel J. , Steimer P. 
Published: March 2011

AbstractQuelques progrès de l'instrumentation dans l'infrarouge lointain ont permis de préciser les constantes optiques de CdSe, ZnTe et ZnSe par des mesures de transmission ou de réflexion à la température de l'hydrogène liquide, de l'azote liquide et à température ordinaire. I. ‐ Les spectres de réflexion d'un polycristal de CdSe, d'une pastille de ZnTe, et d'une lame d'Irtran 4 (ZnSe) obtenus à 290 et 80°K, s'analysent de façon satisfaisante dans l'hypothèse de deux oscillateurs de Lorentz pour CdSe, et d'un seul pour ZnTe, et ZnSe. a) Pour CdSe à 290°K, on trouve ν1 = 171 cm−1, ν2 = 190 cm−1. Seule, la première fréquence est à retenir. La deuxième, bien que nécessaire pour retrouver le spectre de réflexion observé, proviendrait de traces de soufre dans l'échantillon. On en déduit la fréquence longitudinale optique νLO = 214 cm−1, et le rapport de la charge effective des ions à celle de l'électron dans la théorie de Szigetti: e*/e = 0,85. A 80°K, on a ν1 = 175 cm−1 et νLO = 219 cm−1. b) Pour ZnTe à 290°K, on trouve ν1 = 177 cm−1; νLO = 205 cm−1; e*/e = 0,67. A 80°K, ν1 = 181 cm−1; νLO = 209 cm−1. c) Pour ZnSe à 290°K, ν1 = 204 cm−1, νLO = 254 cm−1, e*/e = 0,78. A 80°K, ν1 = 211 cm−1; νLO = 257 cm−1. II. ‐ La transmission d'une couche très mince de ZnSe évaporée sur quartz permet de retrouver ν1 = 204 cm−1 à 290°K, ainsi qu'une valeur approchée du maximum de l'indice d'absorption kmax ≈︁ 5. Par ailleurs, la transmission d'une lame épaisse de ZnSe à la température de l'hydrogène liquide permet de mettre en évidence quatre bandes d'absorption secondaire à 20; 23; 26,8 et 71 μm. La bande très faible à 20 μm est attribuée à une combinaison de trois phonons: LO + TO + TA. Les trois autres bandes sont interprétées par des combinaisons à deux phonons, respectivement: LO + TO, LO + LA et 2 TA. On en déduit: TA = 70,5 cm−1; LA = 149 cm−1; TO = 210 cm−1 et LO = 225 cm−1. On voit que les valeurs de LO et TO à la limite de la zone de Brillouin sont voisines, comme le fait prévoir la valeur de e*/e et la règle de Keyès [24].
Z1‐ and Z2‐centres in mixed crystals of alkali halides doped with Sr++
Authors: Hingsammer J. , Jodl H. 
Published: March 2011

AbstractIn mixed single crystals of KCI‐RbCl: Sr and KCI‐KBr: Sr of various composition grown by the Kyropoulos‐Method Z1‐and Z2‐centres are produced by additive coloration and bleaching. Thus the influence of the substitution of the anions and cations on the spectral position and halfwidth of the Z1‐and 2‐bands can be investigated investigated. In the mixed crystals the spectral position of all absorption bands deviates from the Mollwo relation (v dn = const) in a different manner for anion and cation substitution. The deviations are similar to those found by Smakula for V1‐centres. The halfwidth of all bands in mixed crystals is greater than in pure systems, and the halfwidth of the Z1‐centres increases by ion substitution more than that of the Z2‐centres. The halfwidth of the 1:1 composition of KCl‐RbCl:Sr and KCl‐KBr:Sr is calculated using the model of Gnaedinger and compared with the measured data.
Variation of the refractive indices of calcite, with pressure to 7 kbar
Authors: Davis T. A. , Vedam K. 
Published: March 2011

AbstractThe variation of the ordinary and extraordinary refractive indices of calcite for λ = = 5893 Å with hydrostatic pressure to 7 kbar has been measured from the shift of the localized interference fringes across the sample which was kept in a fluid pressure medium. The change in the thickness of the sample under pressure was considered by utilizing the non‐linear theory of elasticity. The ordinary and the extraordinary refractive indices were found to increase linearly with pressure with slopes of 0.50 × 10−3/kbar and 0.44 × 10−3/kbar respectively in the entire region investigated. The results are compared with the theoretical values evaluated from Bragg's theory, and are also interpreted according to Mueller's theory of photoelasticity.
Elektronenmikroskopie von Gleitlinien auf verformtem NaCl
Authors: Matucha K.‐H. 
Published: March 2011

AbstractGleitlinien auf plastisch verformten [001]‐ und [011l‐orientierten NaCl‐Einkristallen werden elektronenmikroskopisch untersucht. Die Abgleitung erfolgt bevorzugt auf zwei zueinander orthogonalen Systemen. In Bereich II der VK werden schräg dazu liegende Dodekaeder‐Systeme mitbetätigt. Bei der [011]‐Orientierung findet zusätzlich Gleitung auf {100}‐Ebenen statt, wodurch die Orientierungsabhängigkeit der VD erklärt werden kann. Bereich III der VK ist durch Quergleiten von Schraubenversetzungen auf . Die Gleitlinien der beiden bevorzugt betätigten Dodekaeder‐Systeme zeigen nach Höhe und Länge eine große Ähnlichkeit mit denen auf für Einfachgleitung orientierten k.f.z. Metallen. Aus den Ergebnissen der Gleitlinienuntersuchungen läßt sich nach Seeger die Steigung der VK in Bereich II berechnen.
Versetzungsecken in Kubisch‐flächenzentrierten Kristallen: Teil I: Die Geometrie der Versetzungsecken
Authors: Differt K. 
Published: March 2011

AbstractEs werden bisher in der Literatur nicht diskutierte Versetzungskonfigurationen vorgestellt. die in kubisch‐flächenkonzentrierten Kristallen auftreten können. Die Konfigurationen bilden sich an zwei sich treffenden Kantenversetzungen, welche in verschiedenen <110>‐Richtungen verlaufen. Die möglichen Arten dieser Konfigurationen werden zusammengestellt und auf ihre Stabilität untersucht. Bestimmte Arten zeigen einen ausgedehnten Stapelfehler, der zwischen den Kantenversetzungen aufgespannt wird.
Paramagnetic resonance of copper atoms stabilized in alkali‐halide crystals
Authors: Zhitnikov R. A. , Koltsov V. B. , Melnikov N. I. 
Published: March 2011

AbstractStabilized copper atoms are obtained at 77°K by irradiating alkali halide crystals (LiCl, NaCl and KCl) containing monovalent copper ions with X‐rays. The properties of these stabilized atoms are studied by PR (paramagnetic resonance). In the paramagnetic resonance spectra a super‐hyperfine structure is observed indicating a substitutional position of the stabilized copper atoms in the cubic lattice of the alkali halide crystals. An interpretation of the data obtained is given.
Time‐of‐flight neutron spectroscopy: a new application of aerodynamic sample levitation
Authors: Kozaily Jad , Hennet Louis , Fischer Henry E. , Koza Marek , Brassamin Séverine , Magazù Salvatore , Kargl Florian 
Published: March 2011

AbstractA new version of a laser‐heated aerodynamic levitation apparatus that enables the study of high temperature liquids by neutron spectroscopy is presented. This levitator was developed to be used on the IN6 neutron TimeOf‐Flight (TOF) spectrometer at the European High Flux Neutron Source of the Institute Laue Langevin (ILL) in Grenoble, France. This device overcomes earlier restrictions to small sample sizes as routinely used for neutron diffraction studies on levitated liquids at high temperature, and makes other improvements in signal‐to‐noise ratio. A factor of more than three increase in sample volume in combination with the high flux and low background instrument IN6 makes quasielastic neutron scattering (QENS) studies on levitated molten oxides feasible. Here, we present results of a first QENS experiment towards the study of the relaxation dynamics of a molten CaO‐Al2O3 sample. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Oxygen diffusion into GaN from oxygen implanted GaN or Al2O3
Authors: Jakiela Rafal , Dumiszewska Ewa , Caban Piotr , Stonert Anna , Turos Andrzej , Barcz Adam 
Published: March 2011

AbstractThermal diffusion and incorporation of oxygen in gallium nitride during MOVPE growth process was investigated using secondary ion mass spectroscopy. The source of oxygen were (18O) implanted into GaN or Al2O3 substrate. Experiment shows no oxygen diffusion from Ar‐implanted sapphire or O‐implanted GaN and extremely deep diffusion from O‐implanted sapphire. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of elastic energy on the spinodal decomposition in InAlGaN materials
Authors: Diaz Albarran Salvador F. , Rodriguez Peralta Patricia 
Published: March 2011

AbstractThe purpose of our study is to determine the influence of elastic energy on the spinodal decomposition ranges of InAlGaN alloys lattice‐matched to GaN. The distinction in lattice constants of the binary compounds constituting these alloys gives rise to their deformation energies. Such energies provide the tendency to disintegration that can lead to an appearance of the thermodynamically unstable states with respect to the decomposition. The initial stage of spinodal decomposition of the InAlGaN quaternary alloys is accompanied by transfers of atoms over distances of a lattice parameter. Accordingly, these transfers produce a thin two‐layer region with negligibly small differences in their compositions. Formation of these layers causes the elastic energy. The alloys are represented as quaternary regular solutions. The internal deformation energy is calculated with the interaction parameters estimated by the valence force field model. The spinodal decomposition ranges of these materials are demonstrated up to 580 °C (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Theoretical study on the influence of surface hydrogen coverage on the initial growth process of AlN(0001) surfaces
Authors: Suzuki Hikari , Murakami Hisashi , Kumagai Yoshinao , Koukitu Akinori 
Published: March 2011

AbstractThe adsorption processes of group‐V sources used in metalorganic vapor phase epitaxy (MOVPE) and hydride vapor phase epitaxy (HVPE) were investigated using first‐principle calculations based on the density functional theory (DFT) to understand the initial growth process of AlN(0001). To examine the influence of surface hydrogen coverage on the initial growth process, the ideal surface and a reconstructed surface with an adsorbed 0.75 monolayer of hydrogen were used as the initial surface structures. NH3 and NH2 generated by the decomposition of NH3 were considered as group‐V sources. From the calculations, the influence of surface hydrogen coverage on the initial growth process of AlN(0001) surfaces in vapor phase epitaxy was clarified. It was revealed that surface hydrogen coverage does not have an effect on adsorption of NH3, whereas NH2 was affected by hydrogen on the surface. It was also demonstrated that the adsorption energies for NH3 and NH2 on the ideal and reconstructed GaN(0001) surfaces are smaller than those on the ideal and reconstructed AlN(0001) surfaces (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Measurements of generation‐recombination effect by low‐frequency phase‐noise technique in AlGaN/GaN MOSHFETs
Authors: Kayis Cemil , Leach Jacob H. , Zhu C.Y. , Wu Mo , Li X. , Özgür Ümit , Morkoç Hadis , Yang X. , Misra Veena , Handel Peter H. 
Published: March 2011

AbstractGeneration‐recombination processes in AlGaN/GaN metal‐oxide‐semiconductor heterostructure field‐effect transistors (MOSHFETs) with HfAlO gate dielectric has been investigated through low‐frequency phase‐noise. Some devices tested exhibited noise spectra deviating from the well‐known (1/fγ)spectrum. These devices showed broad peaks attributed to generation‐recombination (GR) in the noise‐spectral‐density vs. frequency plots, which shifted toward higher frequencies at elevated temperatures. The unannealed and annealed MOSHFETs exhibited trap energy values as 0.22 eV and 0.11 eV at drain bias values of 6.3 V and 10 V, respectively. We also monitored the effect of source‐drain bias on the excess GR noise. The time constant of the traps decreased from 16.7 ms to 2.1 ms as we increased the VDS from 10 V to 18 V for the annealed devices. This effect can be explained by the potential barrier lowering (Frenkel‐Poole effect) of the traps by electric field (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth of GaN based structures on focused ion beam patterned templates
Authors: Cordier Y. , Tottereau O. , Nguyen L. , Ramdani M. , Soltani A. , Boucherit M. , Troadec D. , Lo F.‐Y. , Hu Y. Y. , Ludwig A. , Wieck A. D. 
Published: March 2011

AbstractFocused ion beam technique is a powerful tool for defining patterns within a semiconductor film. In this paper, we show that it is possible to realize patterns such as disks and columns within thick GaN templates and that it is compatible with the regrowth of GaN based heterostructures. We study the effect of the pattern size and shape on the regrowth by molecular beam epitaxy. We show that the growth using ammonia as the nitrogen source with flux at temperature optimized for 2‐dimensional growth leads to the apparition of well defined growth planes. We show that the development of these planes is dependent with the initial pattern size and shape. These results confirm the difficulty for realizing micro or nano‐columns with axial heterostructures. At the opposite, these growth conditions seem favourable for core‐shell heterostructures column with well defined m‐plane and eventually a‐plane lateral facets. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the reduction of efficiency loss in polar c ‐plane and non‐polar m ‐plane InGaN light emitting diodes
Authors: Li X. , Ni X. , Liu H. Y. , Zhang F. , Liu S. , Lee J. , Avrutin V. , Özgür Ü. , Paskova T. , Mulholland G. , Evans K. R. , Morkoç H. 
Published: March 2011

AbstractWe have undertaken a series of experiments in InGaN light emitting diode (LED) structures both on polar (c‐plane) and non‐polar (m‐plane) GaN substrates with and without magnesium doped AlGaN electron blocking layers (EBLs) on the p‐side of the p‐n junction to shed the much needed light on the carrier injection and transport. The LEDs grown on c‐plane bulk GaN substrates without EBL show 40% peak electroluminescence (EL) intensity, while the EL peak intensity of the LEDs grown on m‐plane bulk GaN substrates without EBL is 30% of that with EBL. However, optical measurements for internal quantum efficiency (IQE) reveal that the IQE values of LEDs with and without EBL are comparable for both cases, which are in the range of 80‐85% for m‐plane variety and 50% for c‐plane variety. Furthermore, with varying Al composition (15%, 8%, 0%) in the EBL, the EL intensity for both m‐pane and c‐plane LEDs decrease progressively as the Al composition decreases. When highly conductive and transparent Ga doped ZnO layers are used as the current spreading layers for LEDs, the degradation of the efficiency with injection is significantly reduced to 27% compared to LEDs with semitransparent Ni/Au contacts having 50% efficiency degradation up to the same current density ∼3500 A/cm2. This can be due to presumably the reduction in current filamentation or current crowding. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Depth profile of residual strain in free‐standing GaN substrates measured by cross‐sectional micro‐reflectance spectroscopy
Authors: Yamaguchi A. A. , Geng H. Y. , Sunakawa H. , Sumi N. , Yamamoto K. , Usui A. 
Published: March 2011

AbstractDepth profiles of residual strain in free‐standing GaN substrates have been successfully measured by a novel method employing cross‐sectional micro‐reflectance spectroscopy. This method can precisely measure very small strains (∼0.01%) with micron‐order spatial resolution. In addition, we have established a theoretical framework to calculate the depth profiles of intrinsic strain, which cause the bending of substrates, from the measured residual strain in bending substrates. These methods were applied for hydride vapour phase epitaxy (HVPE)‐grown free‐standing GaN crystals fabricated by two different facet‐initiated epitaxial lateral overgrowth (FIELO) techniques, and it is found that the intrinsic strain can be controlled by the FIELO technique. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
GaN boules grown by high rate HVPE
Authors: Richter E. , Gründer M. , Schineller B. , Brunner F. , Zeimer U. , Netzel C. , Weyers M. , Tränkle G. 
Published: March 2011

AbstractThe most promising approach for GaN substrate fabrication on the base of HVPE consists in the growth of thick GaN crystals and subsequent cutting of these boules into slices followed by conventional surface preparation. This work focusses on a HVPE GaN boule growth process optimized to highest growth rate and the use of a commercially available vertical HVPE reactor from AIXTRON in order to develop a technology of high productivity to enable low‐cost substrates. To this end, GaN crystals up to thicknesses of 6.3 mm have been grown on 2 inch GaN‐on‐sapphire templates produced by MOVPE. The rate in HVPE growth was 450 µm/h and the material properties of the crystals have been evaluated. No degradation of the material quality was found by comparison of structural, optical and transport properties with published data of the state of the art of bulk GaN. Dislocation densities as low as 6x105 cm‐2, high electron mobility of 960 cm2/Vs for a carrier density of 1x1016 cm‐3, low background impurity incorporation of oxygen and silicon, luminescence with well resolved excitonic emission, and a high value of thermal conductivity of 294±44 W/mK were determined. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Patterning of sapphire/GaN substrates
Authors: Suihkonen S. , Ali M. , Svensk O. , Sintonen S. , Sopanen M. , Lipsanen H. , Törmä P. T. , Nevedomsky V. , Bert N. 
Published: March 2011

AbstractWe present the results of sapphire/GaN substrate patterning on GaN film quality and on LED performance. MOVPE was used to grow GaN films on c‐plane sapphire. The films were then patterned with hexagonal holes with various diameters. When regrown with GaN, voids were formed in the sapphire/GaN interface. The void shape could be controlled from nearly vertical to inclined by changing the pattern dimensions. Patterning resulted also in reduced dislocation density of the overgrown GaN film. X‐ray diffraction and transmission electron microscopy results showed that the reduction is due to bending of edge‐type dislocations during the regrowth of the patterned substrate. Standard LEDs were grown on reference and patterned substrates and processed into chips. When grown on a patterned substrate LED chips showed approximately 10% increase in light output when compared to ones grown on a reference sample. The increase was attributed to improved light extraction. More improvement can be expected by optimizing the pattern geometry and the void shape. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Far beyond the classical data models: symbolic data analysis
Authors: Noirhomme‐Fraiture Monique , Brito Paula 
Published: March 2011

AbstractThis paper introduces symbolic data analysis, explaining how it extends the classical data models to take into account more complete and complex information. Several examples motivate the approach, before the modeling of variables assuming new types of realizations are formally presented. Some methods for the (multivariate) analysis of symbolic data are presented and discussed. This is however far from being exhaustive, given the present dynamic development of this new field of research. © 2011 Wiley Periodicals, Inc. Statistical Analysis and Data Mining 4: 157–170, 2011