bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relativistic KKR‐calculations on the band structure of selenium and tellurium
Authors: Kramer B. , Thomas P. 
Published: March 2011

AbstractThe influence of relativistic corrections and spin‐orbit coupling in the band structure of selenium and tellurium is calculated using the relativistic Korringa‐Kohn‐Rostokermethod. The symmetrized central‐field spinors are given. The 11 μm‐band of tellurium is explained by spin‐orbit splitting at the upper valence band edge at H.
Climb of extrinsic faults in silicon
Authors: Dash S. , Joshi M. L. 
Published: March 2011

AbstractFrank hexagonal loops, extrinsic stacking faults, and misfit dislocations can be generated through diffusion of very high concentrations of As in silicon. If a thin film of silicon containing such extrinsic faults and dislocations is quenched, the quenched‐in vacancies annihilate the stacking faults at the locations where dislocations approach the faults. This paper discusses the probable mechanism of such fault annihilation.
On the effective recombination cross‐section of charged centres in crystal phosphors
Authors: Antonov‐Romanovskii V. V. 
Published: March 2011

AbstractThe effective recombination cross‐section σeff of charged centres measured experimentally is found to be not always equal to the gas kinetical cross‐section σk. σeff is also dependent on the diffusion coefficient D and mobility μ. Such a dependence is enhanced at small free pass length l. In a general case the relation holds σk≦ σeff≦ σμ MD (where σμ is the pure drift cross‐section and MD is multiplication constant due to diffusion; σμ = (4 π R′l)/3, where R′ is the distance at which the potential energy of the free charge in the field of the centre becomes equal to kT). At small σk a temperature dependence can arise with “negative” activation energy σeff ∼ e−E/kT, where E < 0. The limiting case σeff = σk is not trivial because the equality is due to original mutual compensation of drift and diffusion.
Direct observations of plane wave and spherical wave Pendellösung fringes
Authors: Hart M. , Milne A. D. 
Published: March 2011

AbstractBy using successive Bragg reflections in a monolithic block of effectively perfect silicon, both plane wave (Ewald type) and spherical wave (Kato type) Pendellösung fringes have been obtained in the same wedge‐shaped crystal. In agreement with the theories, the fringe spacings are the same only at the centre of Bragg reflection and the fringe positions are different in the two cases.
Thermally activated dislocation motion in a solid containing a multiple spectrum of dislocation obstacles
Authors: Frank W. 
Published: March 2011

AbstractA theoretical treatment is given of the thermally activated motion of dislocations in the presence of dislocation obstacles with different hardness. The hardness of an obstacle is allowed to depend on an arbitrary number of characteristic parameters (multiple obstacle spectrum). It is shown that even under these conditions the slip rate ȧ obeys an Arrhenius equation mean free activation enthalpy. The general theory is applied to the case of plastic flow in neutron‐irradiated copper. In this case the dislocation obstacles are vacancy dislocation loops of different sizes, different orientations, and different distances from the slip planes of the mobile dislocations (triple spectrum).
N‐ and S‐type negative resistances and relaxation oscillations in Au‐doped double injection Ge diodes
Authors: Hennig H.‐P. 
Published: March 2011

AbstractIn the course of investigations of Au‐doped double injection Ge diodes with a 0.15 eV level partially populated at thermal equilibrium, a voltage‐controlled negative resistance was observed below 65°K before the current‐controlled S‐type negative resistance occurring with DI diodes becomes important. The creation of N‐type negative resistance can be explained by an occupation of the 0.2 eV gold level, while the generation of oscillations must be related to the creation of the S‐type negative resistance [5].
Charge compensation of trapped holes in silver bromide
Authors: Buroff A. , Malinowski J. 
Published: March 2011

AbstractThe temperature dependence of the hole photoresponse in silver bromide single crystals is measured in the temperature range 200 to 300°K. The bulk lifetime of photoexcited holes is shown to pass through a minimum at temperatures where the drift mobility exhibits a maximum value. The analysis of the experimental results suggests that the lifetime of holes is limited by a neutralization process, presumably by silver ion vacancies, preceded by multiple trapping at a level 0.41 eV above the valence band. The proposed scheme is in accordance with other experimental results concerning the properties of holes in silver bromides.
Optical study on the ferroelectric orthorhombic phase of Fe‐I‐boracite
Authors: Kobayashi J. , Schmid H. , Ascher E. 
Published: March 2011

AbstractThe ferro‐electricity of the Fe‐I‐boracite is confirmed by the direct observation of domain‐switching. By using this phenomenon, the birefringence in the three principal sections of the indicatrix is measured as a function of temperature. The abrupt and large change of the electrostrictive nature along the ferroelectric axis at the ferro‐electric transformation is demonstrated.
On the trap distribution in thin films of copper phthalocyanine
Authors: Hamann C. 
Published: March 2011

AbstractThin films of copper phthalocyanine are found to be intrinsic semiconductors with an energy gap of 1.98 eV. Their electric properties at high fields are determined by an exponential trap distribution. The form of the distribution and its parameters are determined by SCLC‐measurements, the discret character of the trap level spectrum by back current measurements. All results may be interpreted by assuming a model of an isotropic nondegenerate semiconductor whose effective hole mobility is higher than the effective electron mobility.
Spin density oscillations in a polarized free electron gas
Authors: de Chatel P. , Szabó I. 
Published: March 2011

AbstractThe wave‐number dependent dynamic susceptibility of a uniformly polarized free electron gas is calculated. Due to the polarization the spin density oscillations around a sharply localized magnetic impurity are modified both in phase and amplitude. The oscillations in the totally magnetized state are enhanced by about 20 percent, but in intermediate states they are smaller than in the unmagnetized system.
A study of quench hardening in copper
Authors: Davidson J. L. , Galligan J. M. 
Published: March 2011

AbstractQuenching studies of copper, under clean conditions, have revealed a two stage hardening mechanism. The first stage corresponds to the formation of small vacancy clusters and occurs around room temperature, while the second stage is centered around 250°C. Measurements of the dislocation loop density in quenched, aged specimens in the second stage of hardening, show that Frank vacancy loops are the major obstacle to dislocation motion. The temperature dependence of the critical resolved shear stress, in quenched specimens, was also measured throughout the aging process and compared with various expressions for the interaction of mobile dislocations with different obstacles. These results indicate quite clearly that Seeger's theory of obstacle shearing is favored over Fleisher's theory of asymmetrical distortion in this case. An experimental value of the cutting process is about 5 eV. In agreement with this mechanism, electron microscope observations show that Frank dislocation loops, within a slip plane, are removed during the first few percent of plastic deformation. Finally, the quench hardening is only removed at very high temperatures, in the same temperature range where the Frank loops are removed.
Recrystallization of cold‐worked gold during α‐irradiation
Authors: Beyer H. , Sizmann R. 
Published: March 2011

AbstractThe recrystallization of gold is investigated by electrical resistivity measurements and checked with photomicographs. The influence of irradiation with 4 Me V α‐particles at different temperatures and flux densities is studied. Between 100 to 150°C the recrystallization of Au (purity 99.96%) is enhanced during irradiation. With increasing irradiation dose the enhanced reaction rate is overcompensated by a strong retardation of the grain growth. The enhancement is attributed to radiation‐induced diffusion, the retardation to barrier pinning of dislocations, and grain boundaries.
Zinc‐blende (cubic) GaN bulk crystals grown by molecular beam epitaxy
Authors: Novikov S. V. , Foxon C. T. , Kent A. J. 
Published: March 2011

AbstractWe have studied the growth of zinc‐blende (cubic) GaN and AlxGa1‐xN layers and bulk crystals by molecular beam epitaxy (MBE). MBE is normally regarded as an epitaxial technique for the growth of very thin layers with monolayer control of their thickness. However, we have used the MBE technique for bulk crystal growth and have produced GaN layers up to 100 μm in thickness. Thick, cubic GaN films were grown on semi‐insulating GaAs (001) substrates by a modified plasma‐assisted molecular beam epitaxy (PA‐MBE) and were removed from the substrate after the growth. The resulting free‐standing GaN wafers with thicknesses in the 30–100 μm range may be used as substrates for further epitaxy of cubic GaN‐based structures and devices. We have demonstrated the scalability of the process by growing GaN layers up to 3” in diameter. We have developed procedures to cleave the wafers and to polish them to produce epi‐ready surfaces. We have demonstrated that the PA‐MBE process we have developed also allows us to achieve free‐standing zinc‐blende AlxGa1‐xN wafers over the entire composition range from GaN to nearly pure AlN. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
InGaN based light emitting diodes utilizing Ga doped ZnO as a highly transparent contact to p‐GaN
Authors: Liu H. Y. , Li X. , Liu S. , Ni X. , Wu M. , Avrutin V. , Izyumskaya N. , Özgür Ü. , Yankovich A. B. , Kvit A. V. , Voyles P. M. , Morkoç H. 
Published: March 2011

AbstractWe report on the electrical and optical properties of InGaN based light emitting diodes (LEDs) utilizing Ga doped ZnO (GZO) grown by MBE as a highly transparent contact p ‐electrode (GZO‐LEDs). For comparison, the LEDs with semi‐transparent thin Ni/Au (5nm/5nm) current spreading layers were also fabricated on the same wafer (Ni/Au‐LEDs). Pulsed electroluminescence measurements revealed that the relative external quantum efficiency (EQE) of the GZO‐LED is 1.7‐2 times higher than that of Ni/Au‐LED at high current densities. Moreover, GZO‐LEDs can withstand much higher current densities (4700 A/cm2) than the Ni/Au LEDs (3500 A/cm2) under pulsed mode. Unpackaged GZO‐LEDs with 200 μm diameter showed negligible light output degradation for up to 30 mins under CW current of 100 mA (corresponding to a 318 Acm‐2 current density), while the light output for Ni/Au‐LEDs was reduced by 85% after only 5 mins of operation due to the severe current crowding effect (or current filamentation). (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Empirical potential approach to the epitaxial relationship between AlN thin films and Si(001) substrates
Authors: Ito Tomonori , Nakano Haruo , Akiyama Toru , Nakamura Kohji 
Published: March 2011

AbstractEpitaixial relationship between AlN thin films and Si(001) substrates is systematically investigated using the empirical interatomic potential on the basis of the experimental findings for AlN on Si(001) grown by plasma‐assisted molecular beam epitaxy and reactive magnetron sputtering. The calculated results for the structural stability of AlN on Si(001) reveal that (0001)‐oriented 2H‐AlN becomes stable even on 3C‐Si(001) beyond the film thickness of six monolayers with epitaxial relationship of AlN〈01‐10〉‖Si[110]. This is consistent with the experimental results found in plasma‐assisted molecular beam epitaxy. We also estimate the relative appearance ratio among various rotational domains with AlN〈11‐20〉‖Si[110] (Type A) and AlN〈01‐10〉‖Si[100] (Type B) in addition to the AlN〈01‐10〉‖Si[110] (Type C). The calculated appearance ratio such as 23.7% (Type A), 30.7% (Type B), and 14.8% (Type C) are favourably compared with respective experimental results such as 24.7%, 26.5%, and 22.8% obtained by reactive magnetron sputtering. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Scanning near‐field luminescence microscopy of green light emitting GaInN/GaN quantum wells grown on c‐plane sapphire and on c‐plane bulk GaN
Authors: Clodius P. , Jönen H. , Bremers H. , Rossow U. , Hangleiter A. 
Published: March 2011

AbstractIn contrast to blue and violet emitting GaInN quantum well structures grown on sapphire, which show a high internal quantum efficiency (IQE), green emitting structures suffer from relatively low efficiencies. Usually, the large internal polarization fields are made responsible for such reduced efficiencies. For quantum wells with high In content, however, the efficiencies are even lower than expected.In this work we present the results of our near‐field optical investigations of the photoluminescence of green emitting GaInN quantum well structures grown on c‐plane sapphire and on bulk GaN substrates. Our aim is to clarify the influence of defects on the spatial structure of the luminescence of green emitting quantum wells. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Polarity control of AlN by poling in the crystal growth
Authors: Ota Yuichi , Inushima Takashi 
Published: March 2011

AbstractWe present a new technique for controlling the polarity of AlN grown by metal‐organic chemical vapor deposition on sapphire. We apply electric field along the c‐axis throughout the crystal growth process and Al‐ or N‐polarity AlN is obtained according to the direction of the electric field.It turns out that the polarization of pyroelectric AlN can be changed by the external field applied at the initial growth stage. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Calculation of phase diagrams of the Li3N‐Al system for AlN growth
Authors: Yayama Tomoe , Kangawa Yoshihiro , Kakimoto Koichi 
Published: March 2011

AbstractTo investigate the possibility of AlN synthesis from Li3N and Al as source materials, a phase diagram of the Li3N‐Al system was constructed by using calculation of the phase diagram (CALPHAD) method. Thermodynamic data of a ternary system was prepared on the basis of data of binary systems, which are Al‐Li, Al‐N and Li‐N. In the present work, we newly incorporated thermodynamic data of Li3AlN2 into the system. Gibbs energy function of Li3AlN2 is described by a stoichiometric compound model and the parameter was determined to reproduce our experimental results. The calculated phase diagram was verified by differential thermal analysis (DTA). The calculated solution temperature of Li3AlN2 agreed with the DTA results and the validity was confirmed. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of sputtering conditions on crystalline quality of AlN layers deposited by RF reactive sputtering
Authors: Kumada Tomoyuki , Ohtsuka Makoto , Takada Kazuya , Fukuyama Hiroyuki 
Published: March 2011

AbstractAluminum nitride (AlN) is increasingly demanded for use in semiconductor‐related industries. This study was undertaken for fabrication of high‐quality AlN thick layers using radio‐frequency (RF) reactive sputtering with a pure Al target. The AlN layers were sputtered homoepitaxially on high‐quality thin AlN layers on sapphire substrates for 1.5 h with 300 to 650 W at 573 and 773 K. The AlN thin layers were grown using sapphire nitridation before sputtering. A N2‐Ar gas mixture was used as the sputtering atmosphere and N2 gas flow ratio was changed from 20 to 60 vol%N2. In all sputtering conditions c‐axis oriented AlN layers were fabricated. AlN layer sputtered with 400 W under 40 to 60 vol%N2 at 773 K was grown by about 1 μm thickness. The AlN layer sputtered with 400 W under 40 and 50 vol%N2 at 573 and 773 K showed superior quality, with almost identical crystal structural quality to that of each nitrided sapphire substrate. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Reliability and performance of pseudomorphic ultraviolet light emitting diodes on bulk aluminum nitride substrates
Authors: Grandusky James R. , Gibb Shawn R. , Mendrick Mark , Schowalter Leo J. 
Published: March 2011

AbstractHigh quality, bulk aluminum nitride substrates were used to obtain pseudomorphic AlxGa1‐xN layers with low dislocation density, smooth surfaces, and high conductivity. These layers were fabricated into mid‐ultraviolet light emitting diodes with peak wavelengths in the range of 240‐260 nm. From transmission electron microscope images, it was confirmed that the dislocation density in the n‐type Al0.7Ga0.3N layer is low with no dislocations in the field of view. The low dislocation density continued through the quantum wells and electron blocking layer. However, the lattice mismatch between the pseudomorphic AlxGa1‐xN layers and the p‐type GaN contact layer is high (approximately 2.4%) and the pseudomorphic growth could not be achieved for thick layers. Instead, a network of misfit dislocations was formed at the GaN/AlxGa1–xN interface, which relieved strain in the GaN layer. The threading dislocations did not appear to propagate into the active region and thus enable the achievement of high internal (IQE) and external quantum efficiencies (EQE) from the devices fabricated on low dislocation density pseudomorphic active layers. Values of EQE as high as 1.44% for a device emitting at 248 nm operated in pulsed mode were achieved. Devices were packaged in lead frame packages and achieved output powers of 45 mW at 1.5 A for a 257 nm device with a peak EQE of 0.8% at 200 mA when operated in pulsed mode. The thermal properties of the packaged devices limited high current performance in CW mode. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Epitaxial growth of β‐Si3N4 by the nitridation of Si with adsorbed N atoms for interface reaction epitaxy of double buffer AlN(0001)/β‐Si3N4/Si(111)
Authors: Yamabe Nobuhiko , Yamamoto Yuka , Ohachi Tadashi 
Published: March 2011

AbstractA fabrication process of an interface reaction epitaxy (IRE) β‐Si3N4 and an IRE AlN were investigated to produce a double buffer layer (DBL) of AlN(0001)/β‐Si3N4/Si(111) for the growth of group III nitrides films on Si. The β‐Si3N4 was formed by using adsorbed (ADS) nitrogen atoms irradiated indirectly from a rf‐plasma cell. Two surface structures of the β‐Si3N4, which were “8 x 8” and “8/3 x 8/3” reconstructions, were fabricated by changing the nitrogen irradiation conditions; complete and incomplete nitridation of Si surface and successive heat treatment up to 875 °C formed the “8 x 8” and “8/3 x 8/3” structures, respectively. IRE AlN was grown by 1 monolayer of Al deposition on the β‐Si3N4 and successive annealing at 875 °C. Al and N polarity DBLs were grown on the “8 x 8” and “8/3 x 8/3” structures, respectively. These results indicated that the polarity of DBL could be controlled by the surface reconstruction of β‐Si3N4 (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Tri‐halide vapor phase epitaxy of GaN using GaCl3 gas as a group III precursor
Authors: Yamane T. , Hanaoka K. , Murakami H. , Kumagai Y. , Koukitu A. 
Published: March 2011

AbstractTri‐halide vapor phase epitaxy (THVPE) of GaN using GaCl3 gas generated by the reaction between metallic Ga and Cl2 gas at the source zone was investigated. From thermodynamic analysis, it was predicted that the driving force for GaN growth by THVPE would be larger than that by conventional mono halide vapor phase epitaxy (HVPE) using GaCl as a group III precursor. From the growth experiments, it was shown that the growth rate of GaN by THVPE was much higher than that by conventional HVPE under the same input partial pressure conditions. It was also revealed that GaN growth is possible at higher temperatures by THVPE. In photoluminescence (PL) and X‐ray diffraction (XRD) measurements, a GaN layer grown by THVPE at 1150 °C has optical properties and crystalline quality superior to that of a GaN layer grown by HVPE at 970 °C (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Molecular beam epitaxy based growth of cubic GaN quantum dots
Authors: Schupp T. , Meisch T. , Neuschl B. , Feneberg M. , Thonke K. , Lischka K. , As D. J. 
Published: March 2011

AbstractZinc‐blende GaN/AlN quantum dots were grown in a molecular beam epitaxy system by two alternative methods. In method A the quantum dots were formed by the Stranski‐Krastanov process, whereas in method B the quantum dots were created by a vapor‐liquid‐solid process, respectively. The density of the Stranski‐Krastanov quantum dots was adjustable in a range of 5 x 109 cm‐2 to 5 x 1012 cm‐2. The density of the quantum dots grown by method B was controllable in the range of 5 x 108 cm‐2 to 5 x 1012 cm‐2. For both methods the samples with a high density of quantum dots have shown strong optical activity in photoluminescence spectroscopy. The emission energy of the quantum dots was tuneable in a range of 3.5 eV to 3.9 eV by alteration of the quantum dot height. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Erratum Efficient solar energy conversion of TiO2 nanotubes produced by rapid breakdown anodization – a comparison [Phys. Status Solidi RRL 1, No. 4, 135–137 (2007)]
Authors: Hahn R. , Stergiopoulos T. , Macak J. M. , Tsoukleris D. , Albu S. P. , Kim D. , Ghicov A. , Kunze J. , Falaras P. , Schmuki P. 
Published: March 2011

AbstractThere is an error in the scale bar of the inset of Fig. 1b in the original manuscript. The corrected figure is presented here in Fig. 1. As the originally used figure (see Fig. 2a here) was not very representative for TiO2 nanotubes grown under the described conditions we now provide a more representative picture (Fig. 2b) confirming an average thickness of ∼2.5 µm (as given throughout the paper). No statement or other scientific content of the article is affected by this correction. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Examining the performance effects of post spin‐off links to parent firms: should the apron strings be cut?
Authors: Semadeni Matthew , Cannella Albert A. 
Published: March 2011

AbstractLittle research has examined the performance implications of the parent‐child relationship post spin‐off. Although the parent provided oversight of the child prior to the spin‐off, effects of post spin‐off links to the child remain unclear. Applying transaction cost and agency theories, our study of 142 firms spun‐off between 1986 and 1997 examines how oversight and ownership by the parent firm influence stock market performance post spin‐off. We find that while child firms benefit from some links to the parent, having too many links is negatively related to performance. The findings suggest that there is a balance between having too much parental involvement and not enough. Our study extends understanding of post spin‐off child firm performance and provides valuable insights for both parent and child firms. Copyright © 2011 John Wiley & Sons, Ltd.
Strategies for Patterning Biomolecules with Dip‐Pen Nanolithography
Authors: Wu Chien‐Ching , Reinhoudt David N. , Otto Cees , Subramaniam Vinod , Velders Aldrik H. 
Published: March 2011

AbstractDip‐pen nanolithography (DPN) is an atomic force microscopy (AFM)‐based lithography technique, which has the ability to fabricate patterns with a feature size down to approximately 15 nm using both top‐down and bottom‐up approaches. DPN utilizes the water meniscus formed between an AFM tip and a substrate to transfer ink molecules onto surfaces. A major application of this technique is the fabrication of micro‐ and nano‐arrays of patterned biomolecules. To achieve this goal, a variety of chemical approaches has been used. This review concisely describes the development of DPN in the past decade and presents the related chemical strategies that have been reported to fabricate biomolecular paterns with DPN at micrometer and nanometer scale, classified into direct‐ and indirect DPN methodologies, discussing tip‐functionalization strategies as well.