bluuebunny/crossref_metadata_2025_split huggingface dataset:
Creating a statewide educational data system for accountability and improvement: A comprehensive information and assessment system for making evidence‐based change at school, district, and policy levels
Authors: Felner Robert D. , Bolton Natalie , Seitsinger Anne M. , Brand Stephen , Burns Amy 
Published: January 2008

AbstractThis article reports on one ongoing statewide effort to create a high‐quality data reporting and utilization system (i.e., High‐Performance Learning Community [HiPlaces] Assessment) to inform educational accountability and improvement efforts system. This effort has undergoing refinement for more than a decade. The article describes the features of this system, particularly how empirically based psychological theory and research informed both the development and the overall design of the assessment method. This system, unlike those used by other educational institutions, is unusual in that from the onset of the development and then the implementation, the assessment moved well beyond the simple assessment of the performance and achievement of students to include a comprehensive assessment of all aspects of the developmental, educational, fiscal, and policy conditions that comprise the ecology of the public education system, at all levels, as well as of the developmental and educational needs and attainment of students. The use of data was integral in guiding specific and ongoing, state‐, district‐, school‐, and classroom‐level improvement plans and efforts, including the development, monitoring, evaluation, and refinement of the program. The major goal that guided this system is, and always has been, the enhancement of schools and students' lives. © 2008 Wiley Periodicals, Inc.
Investigation of Tb‐related green emission in group‐III nitrides by time‐resolved photoluminescence measurement
Authors: Wakahara A. , Takemoto K. , Oikawa F. , Okada H. , Ohshima T. , Itoh H. 
Published: January 2008

AbstractLuminescence properties of Tb impurity in AlGaN are investigated various Al composition using time‐resolved photoluminescence (TRPL). When the AlN molar fraction is increased, the luminescence intensity corresponding to inner‐shell transitions in Tb becomes strong. At low‐temperatures, 5D3–7FJ transitions are dominant in AlN‐rich samples, whereas 5D4–7FJ transitions are dominant at high‐temperature. Temperature dependence of the transient decay and the luminescence intensity suggest thermally activated energy‐transfer process and suppression of energy‐back‐transfer due to widening of the band‐gap. Therefore, the large improvement of PL capability in AlGaN may be due to increase of energy transfer efficiency and/or increase of active Tb impurity. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of Yb impurity on Er‐related emission in Al0.70Ga0.30As:Er,Yb epitaxially grown on GaAs substrate
Authors: Arai Tomoyuki , Uekusa Shin‐ichiro 
Published: January 2008

AbstractThe effects of Yb impurity on the optical properties of an Er,Yb‐implanted Al0.70Ga0.30As epitaxial layer were studied. The defect characterizations were carried out for undoped Al0.70Ga0.30As and Al0.70Ga0.30As:Er,Yb samples annealed in the temperature range from 500 °C to 900 °C. From results of photoluminescence (PL), Raman spectroscopy and positron annihilation spectroscopy, it was found that the implantation damage in Al0.70Ga0.30As:Er,Yb samples are recovered by the thermal annealing at a temperature above 700 °C. Maximum PL intensity of Er‐related emission was observed from the Al0.70Ga0.30As:Er,Yb sample annealed at 800 °C. The energy transfere from Yb3+ to Er3+ was also investigated by selectively excited photoluminescence (PL) and PL excitation spectroscopy. It was also observed that the energy was transfered from Yb3+ to Er3+. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Site‐specific excitation of Eu ions in GaN
Authors: Tafon Penn S. , Fleischman Z. , Dierolf V. 
Published: January 2008

AbstractWe performed cathodoluminescence (CL) studies on Eu‐doped GaN layers that were grown using the Interrupted Growth Epitaxy (IGE) method. We compare these results with our site‐selective combined excitation‐emission spectroscopy (CEES) studies in which numerous Eu3+ incorporation sites can be identified unambiguously. We find that for high beam currents the emission intensity saturates in a way that can only be accounted for by a coexistence of at least two different excitation processes. The ratio in excitation efficiency between these two processes is about 5. This conclusion is supported by the CL spectra which show less pronounced saturation for the majority substitutional incorporation site compared to the defect trap‐related (most likely interstitial) site. We further find that only a small fixed portion of the majority site can be excited through electron bombardment. We explain this behavior with a model for the excitation process in which defects are involved as an intermediate trap of excitation. Energy transfer can occur only to those substitutional Eu ions that are in close proximity to the trap. In the case that the Eu ion defect constitutes the trap itself, the spectra are clearly distinguishable and the transfer rates are highest. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Preparation and photoluminescence of Eu‐doped GaN films by radio frequency magnetron sputtering method
Authors: Shirakata Sho , Yudate Shinji 
Published: January 2008

AbstractThe red‐luminescent Eu‐doped GaN film has been prepared on both sapphire and GaN/sapphire substrates by the conventional RF magnetron sputtering method using a compound powder target (GaN + EuN), N2 sputtering gas and subsequent annealing in NH3. The GaN:Eu layers exhibited a red sharp photoluminescence (PL) line at 622 nm due to 5D0–7F2 transition of Eu3+ ions together with series of narrow PL lines: 5D1–7F1 (540 nm), 5D0–7F1 (580–600 nm), and 5D0–7F3 (665 nm). Dependence of Eu‐related PL on the growth condition is described: Eu‐doping level (EuN in target), substrate temperature (Ts), growth time, and annealing temperature (Ta). The optimum conditions for luminescent GaN:Eu are: (i) the Eu of 2 mol% in target, (ii) Ts at 400–450 °C, and (iii) Ta at 1000 °C for 2 hours. Improvements in intensity and reproducibility of Eu‐related PL have been attained by: (i) the increase of growth time, (ii) the use of undoped GaN buffer layer, (iii) the improvement of the target quality, and (iv) the use of the MOVPE grown GaN/Al2O3 template. Preliminary studies of various PL properties are described: the fine structure in PL spectra, PL decay characteristics, temperature dependence and photoluminescence excitation spectrum (PLE). The PL results are discussed in comparison with those in the GaN:Eu grown by other methods in literature. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Defects in organic electronic devices
Authors: Nguyen T. P. 
Published: January 2008

AbstractThe performance of organic electronic devices depends strongly on the quality of the semiconductor used, and the transport process, in particular is greatly affected by the defect states of the material. Knowledge of trapping parameters is therefore of prime importance for studying organic devices. While defects in conventional semiconductors are well known and can be more or less controlled during processing, the formation of defects in organic materials is still not well understood, and consequently, it is difficult to control the defect states in organic devices. For defects that are electrically active or traps, techniques such as thermally stimulated currents, impedance spectroscopy, or deep level transient spectroscopy have been successfully used for determining the corresponding parameters (density, energy level, capture cross section). In this work, we review some fundamental aspects of trap analysis in organic devices by highlighting their role in the charge transport process in these materials. We present updated data from trap studies in polyfluorene derivative based diodes and we address specific problems in analyzing traps in polymers and organic semiconductors. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electrical characterization of defects introduced in Ge during electron beam deposition of different metals
Authors: Auret F. D. , Coelho S. M. M. , Hayes M. , Meyer W. E. , Nel J. M. 
Published: January 2008

AbstractWe have used deep level transient spectroscopy to characterize the defects introduced in n‐type, Sb‐doped, Ge during electron beam deposition of different metals for Schottky contact formation. We have found that the relative concentration of the electron beam induced defects depended on the metal used: metals that required a higher beam intensity to evaporate, e.g. Ru, resulted in larger defect concentrations than metals that required a lower beam intensity, e.g. Pd. The nature of some of these defects could be established by comparing their properties to those of well‐known defects introduced by electron irradiation of the same material. The most prominent defect thus identified was the E‐center, i.e. the Sb‐V center. This defect forms when vacancies, that are introduced during the interaction of energetic metal and other particles with the Ge surface, diffuse into the Ge where they bond to Sb dopant atoms. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Raman spectroscopy of WO3 nano‐wires and thermo‐chromism study of VO2 belts produced by ultrasonic spray and laser pyrolysis techniques
Authors: Mwakikunga B. W. , Sideras‐Haddad E. , Forbes A. , Arendse C. 
Published: January 2008

AbstractNovel optical and electrical properties of newly synthesized nano‐wires of monoclinic WO3 and nano‐belts of rutile VO2 have been investigated by Raman spectroscopy and thermo‐chromism studies respectively. Phonon confinement is observed in the WO3 nano‐wires and the previously modified Richter equation is fitted to the experimental Raman spectroscopy data to obtain the optical phonon dispersion relations for the 713 cm–1 branch and the 808 cm–1 branch of WO3 phonon spectra for the first time. Electrical measurements on the VO2 nano‐belts at varying temperature reveal an enhanced hysteresis width of about 83 °C surpassing previously reported values on the thermo‐chromism studies on VO2. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical and electronic properties of GaInNP alloys – a new material system for lattice matching to GaAs
Authors: Buyanova I. A. , Chen W. M. , Tu C. W. 
Published: January 2008

AbstractIn this paper we will review our recent results from optical characterization studies of GaInNP. We will show that N incorporation in these alloys affects their structural and defect properties, as well as the electronic structure. The main structural changes include (i) increasing carrier localization due to strong compositional fluctuations, which is typical for all dilute nitrides, and (ii) N‐induced long range ordering effects, specific for GaInNP. The observed degradation of radiative efficiency of the alloys upon increasing N content is attributed to formation of several defects acting as centres of efficient non‐radiative recombination. One of the defects is identified as a complex involving a Ga interstitial atom. N incorporation is also found to change the band line up from the type I in the GaInP/GaAs structures to the type II in the GaInNP/GaAs heterojunctions with [N] > 0.5%. For the range of N compositions studied ([N] ≤ 2%), a conduction band offset at the GaInNP/GaAs interface is found to nearly linearly depend on [N] at –0.10 eV/%, whereas the valence band offset remains unaffected. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photoluminescence under magnetic field and hydrostatic pressure for probing the electronic properties of GaAsN
Authors: Polimeni A. , Pettinari G. , Trotta R. , Masia F. , Felici M. , Capizzi M. , Lindsay A. , O'Reilly E. P. , Niebling T. , Stolz W. , Klar P. J. , Martelli F. , Rubini S. 
Published: January 2008

AbstractThe puzzling electronic properties of GaAsN have been investigated through the compositional dependence of two highly sensitive band structure parameters: the electron effective mass, me, and the electron gyromagnetic factor, ge. In the N concentration range from 0% to 0.7%, both me and ge show a highly nonlinear dependence on N composition that can be explained in terms of alternating on‐ and off‐resonance conditions between the red‐shifting conduction band edge and specific energy‐pinned N cluster states. Furthermore, the electronic properties of the material are studied under hydrostatic pressure, P. This allows tuning in a same sample the interaction between extended and localized states and disclosing a hierarchy between different nitrogen complexes as regards the extent of the perturbation these complexes exert on the electronic properties of the GaAs host crystal. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nanostructure engineering of staggered InGaN quantum wells light emitting diodes emitting at 420–510 nm
Authors: Arif Ronald A. , Ee Yik‐Khoon , Tansu Nelson 
Published: January 2008

AbstractWe demonstrated staggered InGaN quantum wells (QW) grown by metalorganic chemical vapor deposition (MOCVD) as improved active region for visible light emitters. Theoretical studies indicate that staggered InGaN QW with step‐function like In‐content in the well offers significantly improved radiative recombination rate and optical gain, in comparison to the conventional InGaN QW. Experimental results of light emitting diode (LED) structure utilizing staggered InGaN QW show good agreement with theory. Staggered InGaN QW allows polarization engineering leading to improvement of photoluminescence intensity and LEDs output power as a result of enhanced radiative recombination rate. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Editorial: phys. stat. sol. (a) 205/1
Authors: Stutzmann Martin 
Published: January 2008

AbstractHow do you find the scientific information and the manuscript reference you need? The answer to this basic but very important question for every active scientist has changed significantly over the last 30 years. When I was a Ph.D. student or a young postdoc, I would venture regularly to a strange and quiet place called a “library”, where all important journals in my field could be easily identified already from the amount of the shelve space they filled. To find a specific reference and to preserve it for future use was limited by the physical exercise to carry a stack of heavy volumes to the copy machine and to press a “copy” button for each page I really wanted to keep. On the way, sometimes I actually found another interesting paper just by browsing through the latest issue of Journal X, and I copied this one, too. And in most cases, I even read what I copied.Today, things are much better! All relevant information is available online in electronic form, so I do not have to leave my office anymore to find out what's new. The impact factors of journals and the h‐factors of authors help me to distinguish good from bad, or at least that is the hope. Whenever I search for a specific topic, anyhow I will get more hits than I can digest in a realistic time. Fortunately, printers by now are so fast and powerful that I can transfer the rest to a printout which I will, most likely, never use again in the foreseeable future.But seriously, although the way to make use of and to deal with scientific information has changed drastically in the last couple of decades, the basic needs of active scientists for reliable, up‐to‐date, and easily accessible information exchange with their international colleagues worldwide has basically remained the same. We at physica status solidi, therefore, for more than 45 years have been and are dedicated to provide exactly that service to our authors and readers, whether they make use of the pss hardcopies in the library or whether they browse the online files of physica status solidi. Last year, more than 2500 articles have been published after strict peer review and careful editing, which makes physica status solidi (nomen est omen) the second largest journal series in solid state physics. The journal has more than doubled in volume since the year 2000, but the Impact Factor also has increased by a factor of two since 1995, showing that we did not trade in quantity for quality. And, last but not least, the visibility of the journal series as measured by the number of full text downloads has increased by a similar factor of two in the last 24 months alone.In October 2007, more than 40000 full text downloads of physica status solidi articles have been registered by the Wiley Interscience data base. Unfortunately, we have no idea how many of these articles have actually been read …In the name of the entire pss‐team, I thank all of you for your continued support of and interest in physica status solidi and wish you a successful year 2008!
Evidences of the virtual Anderson transition in a narrow impurity band of p‐GaAs/AlGaAs quantum wells: ε4 conductivity and electric breakdown at low temperatures
Authors: Agrinskaya N. V. , Kozub V. I. , Poloskin D. S. , Shamshur D. V. , Chernyaev A. V. 
Published: January 2008

AbstractIn highly doped uncompensated p‐type layers within the central part of GaAs/AlGaAs quantum wells at low temperatures we observed an activated behavior of the conductivity with low activation energies (1‐3) meV which cannot be ascribed to standard mechanisms. We attribute this behavior to the delocalization of hole states near the maximum of the narrow impurity band (characteristic for 2D) in the sense of the Anderson transition. Low temperature conduction ε4 is supported by an activation of minority carriers (resulting from a weak compensation by back‐ground defects) from the Fermi level to the band of delocalized states mentioned above. The corresponding behavior can be specified as virtual Anderson transition. Low temperature transport (<4 K) exhibits also strong nonlinearity of a breakdown type characterized in particular by S‐shaped I‐V curve. The nonlinearity is observed in unexpectedly low fields (<10 V/cm). Such a behavior can be explained by a simple model implying an impact ionization of the localized states of the minority carriers mentioned above to the band of Anderson‐delocalized states. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electron‐electron relaxation in disordered interacting systems
Authors: Bozsoki Peter , Varga Imre , Schomerus Henning 
Published: January 2008

AbstractWe study the relaxation of a non‐equilibrium carrier distribution under the influence of the electron‐electron interaction in the presence of disorder. Based on the Anderson model, our Hamiltonian is composed from a single particle part including the disorder and a two‐particle part accounting for the Coulomb interaction. We apply the equation‐of‐motion approach for the density matrix, which provides a fully microscopic description of the relaxation. Our results show that the nonequilibrium distribution in this closed and internally interacting system relaxes exponentially fast during the initial dynamics. This fast relaxation can be described by a phenomenological damping rate. The total single particle energy decreases in the redistribution process, keeping the total energy of the system fixed. It turns out that the relaxation rate decreases with increasing disorder. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Many electron theory of 1/f ‐noise in hopping conductivity
Authors: Burin Alexander L. , Shklovskii Boris I. , Kozub Veniamin I. , Galperin Yuri M. , Vinokur Valerii 
Published: January 2008

AbstractWe show that 1=f ‐noise in the variable range hopping regime is related to transitions of many‐electrons clusters (fluctuators) between two almost degenerate states. Giant fluctuation times necessary for 1=f ‐noise are provided by slow rate of simultaneous tunneling of many localized electrons and by large activation barriers for their consecutive rearrangements. The Hooge constant steeply grows with decreasing temperature because it is easier to find a slow fluctuator at lower temperatures. Our conclusions qualitatively agree with the low temperature observations of 1=f ‐noise in p‐type silicon and GaAs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Low‐temperature conductance mechanisms in p‐Si/SiGe heterostructures in high magnetic fields
Authors: Drichko I. L. , Dyakonov A. M. , Smirnov I. Yu. , Suslov A. V. , Galperin Y. M. , Vinokur V. , Myronov M. , Mironov O. A. 
Published: January 2008

AbstractLow‐temperature conductance mechanism in low‐density Si/SiGe heterostructures in high magnetic fields (ultra‐quantum limit) is studied using AC and DC transport measurements. Evidence of the Wigner crystal in this regime is given. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Tuning electron‐phonon and Coulomb interactions in organic field effect transistors
Authors: Fratini S. , Morpurgo A. F. , Ciuchi S. 
Published: January 2008

AbstractRecent experiments have demonstrated that the performances of organic FETs strongly depend on the dielectric properties of the gate insulator. In particular, it has been shown that the temperature dependence of the mobility evolves from a metallic‐like to an insulating behavior upon increasing the dielectric constant of the gate material. This phenomenon can be explained in terms of the formation of small polarons, due to the polar interaction of the charge carriers with the phonons at the organic/dielectric interface. Building on this model, it is shown that the Coulomb repulsion between the carriers can lead to a further reduction of the electron mobility at high concentrations, as can be reached in devices with highly polarizable gate dielectrics. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electron hopping‐randomwalk at localized band tail states with exponential density in amorphous hydrogenated silicon
Authors: Murayama Kazuro , Fujisaki Tatuya , Nomura Yukio 
Published: January 2008

AbstractMonte Carlo simulation of hopping‐randomwalk at localized band tail states with the exponential density has been executed. The mean square hopping distance of electrons and the average density of electrons at the starting site after s steps are shown to be given by <r(s)2> ∼ sα and <N(r=0,s)> ∼ s–γ, respectively. The exponents α andγ increase with temperature and reach 1 and 3/2 at high temperatures, respectively. α is shown to be equal to the dispersion parameter, αi, at short time in the time‐of‐flight experiment. The temperature behaviour of α are shown to agree with that of αi in amorphous hydrogenated silicon (a‐Si:H) observed in the electric field lower than 1×104 V/cm. The average depth of electrons and holes in the exponential tail increases with steps and thermally balance at an energy, which is named the hopping‐edge. The temperature dependence of the hopping‐gap, which means the energy difference between electron and hole hopping‐edges, agrees with that obtained from the excitation energy dependence of the luminescence peak energy in a‐Si:H. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)