bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regular ordered gold metallic array and Raman scattering intensification
Authors: Raimundo Daniel S. , Sant'Ana Antonio C. , Fernandez Francisco J. R. , Salcedo Walter J. 
Published: March 2007

AbstractThis paper presents a self‐assembly method for fabrication of regular ordered gold metallic structures, and a study of the local field intensification phenomena in the surface of such structures by the enhanced Raman scattering spectra of the crystal violet molecules adsorbed on the surfaces of these structures. The enhanced phenomena were attributed to the local field intensification at the metallic surface due to surface plasmon modes in the interconnected nano‐sized gold structure within the regular array structures. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A thin‐film field‐emission cathode with Pt or Au interlayer between insulator and Zn0.75Mg0.25O
Authors: Wang Zengmei , Li Dejie 
Published: March 2007

AbstractThe cover picture illustrates a modified design for field emission cathodes proposed by Zengmei Wang and Dejie Li in their Original Paper [1] in the current issue. By introducing an additional interlayer, they were able to significantly improve the symmetry of the cathode's transmission current waveform while maintaining a stable and uniform electron emission.The sketch in the lower part depicts the layer sequence Al/Ta2O5/(Pt or Au)/Zn0.75Mg0.25O/Pt–Au–Ag, where a Pt or Au interlayer is introduced between the insulator (Ta2O5) and semiconductor (Zn0.75Mg0.25O) layers, in order to effectively control the interfacial electron energy state distribution. The resulting transmission current waveforms become completely symmetric (left curves in upper part) in comparison to those of the cathode without metal interlayer (right curves).The first author of the article currently is a Ph.D. candidate at the Electronic Engineering Department of Tsinghua University (Beijing, P.R. China) who is working on electron emission cathodes made of thin films, including discontinuous films.
Preface: phys. stat. sol. (a) 204/4
Authors: Avelino Pasa André 
Published: March 2007

AbstractThis issue contains scientific contributions to the Fifth Brazilian–German Workshop on Applied Surface Science. The workshop was held in Brazil at the beautiful Hotel Portobello, Mangaratiba, a city located 100 km from Rio de Janeiro, from 3–7 April 2006.The meeting was attended by about 80 participants, with 29 invited talks and 43 poster presentations on current topics of surface science.As in previous meetings (1995 in Portobello, RJ, Brazil, 1998 in Döllnsee, Berlin, and 2001 in Itapema, SC, Brazil, 2003 in Ringberg‐Castle, Tegernsee), the program featured contributions to numerous issues in surface science both from the theoretical and the experimental point of view. In the field of materials science, important topics such as catalysis, magnetism, optics and the physics of devices were addressed by describing the structural, physical and chemical properties of nanostructures and films of inorganic (metals, alloys and oxides) and organic (polymers and biological molecules) materials.A substantial part of the success of the meeting is probably due to the relaxed atmosphere at the beach hotel on the green coast of Mangaratiba, where excellent scientific presentations were mixed with intense discussions among both senior and younger researchers.A significant moment came in the opening session, when a presentation in memory of Wolfgang H. P. Losch, his life and scientific achievements, was given by Prof. Horst Niehus. Prof. Losch was the first organizer of this series of meetings together with Prof. Niehus and passed away on 10 August 2004.The organizers of the Workshop, Fernando Lázaro Freire Jr. (Rio de Janeiro, Brazil), Hajo Freund (Berlin, Germany), Antonio Azevedo (Recife, Brazil), Horst Niehus (Berlin, Germany), André A. Pasa (Florianópolis, Brazil) and Eberhard Umbach (Würzburg, Germany), are greatly indebted to the following organizations for financial support: Deutsche Forschungsgemeinschaft (DFG), Fundação Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Finaciadora de Estudos e Projetos (FINEP), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and Universidade Federal de Santa Catarina (UFSC) and the specially created intergovernmental agreement between CAPES and DFG to promote such meetings.March 2007
Kinetic considerations on the phase separation of GaInNAs quantum wells
Authors: Herrera M. , González D. , Hopkinson M. , Liu H. Y. , García R. 
Published: March 2007

AbstractIn this work, the influence of the diffusion process in the phase separation of GaInNAs layers is analyzed. For this, we have studied by TEM GaInNAs/GaAs quantum wells grown at different temperatures in the range 360‐440 °C, finding the existence of periodic strain contrasts in all the wells associated with composition fluctuations in the alloy. These contrasts are more pronounced on increasing the growth temperature, revealing a kinetic influence for the formation of the phase separation. The extrapolation of these results suggests a critical temperature for the beginning of the modulation around 330 °C. The consideration of the growth time and the diffusion time in the epitaxial growth of this alloy suggests that the limiting specie for the formation of the phase separation could be Ga. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ce and Yb doped InP layers grown for radiation detection
Authors: Zavadil J. , Prochazkova O. , Zdansky K. , Gladkov P. 
Published: March 2007

AbstractInP single crystals were grown by liquid phase epitaxy on semi‐insulating InP:Fe substrate with cerium (Ce) and ytterbium (Yb) additions to the growth melt. Grown layers were characterised by Hall measurements and low temperature photoluminescence spectroscopy. Both types of layers exhibit the change of electrical conductivity from n to p type. Ce and Yb have been found to be incorporated into the InP lattice since a sharp luminescence lines arising from inner shell transitions of Yb3+ and Ce3+ were detected at 1002 and 3534 nm, respectively. A metastable conductivity state of InP:Ce layers has been found at temperatures below 35 K, a phenomenon previously reported for InP:Yb layers. Similar electrical behaviour of InP (Ce, Yb) layers leads us to conclude that Ce acts as dominant acceptor impurity responsible for n→p conductivity change. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Approach to reduce the residual strain in bulk InGaAs crystals grown by the multi‐component zone melting method
Authors: Rahman M. S. , Islam M. R. , Alam M. S. , Yamada M. 
Published: March 2007

AbstractAn analytical study has been carried out to evaluate the quantitative amount of strain and its distribution in bulk Inx Ga1–x As crystals grown by the two‐step multi‐component zone melting (MCZM) method. With the combination of Raman scattering, photoluminescence and energy dispersive X‐ray experiments, it has been confirmed that there exists large amount of strain in bulk Inx Ga1–x As crystals grown by the two‐step MCZM method due to approximately exponential variation of composition from 0.06 to 0.29 in the first step growth process. Using an axially symmetrical strain model, the quantitative amount of strain and its distribution have been studied for various compositional profiles including the currently used profile. It has been found that the strain and its distribution are strongly dependent on the shape of the compositional profile. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electro‐optical characterisation for the control of silicon nanocrystals embedded in SiNx:H films
Authors: Lelièvre J.‐F. , Rodriguez H. , Fourmond E. , Quoizola S. , Lipinski M. , Araujo D. , Bremond G. , Lemiti M. 
Published: March 2007

AbstractIn this work, electro‐optical characterization techniques were used to control the size and density of silicon nanocrystals (nc‐Si) in situ grown in non‐stoichiometric amorphous hydrogenated silicon nitride (SiNx:H) films deposited by low‐frequency plasma enhanced CVD (LF‐PECVD). The average crystal size and density of the nc‐Si were measured by HR‐TEM. Photoluminescence (PL) and photocurrent (PC) spectra revealed emission and absorption phenomena related to confined excitons within nc‐Si. By adjusting the deposition parameters, optimum PL and PC responses could be obtained, which are believed to correspond to the highest nc‐Si density combined to an average crystal size equal to or slightly less than 4 nm. Such properties could then be used for the development of high efficiency solar cells. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of graded index SiOxNy antireflection coating for silicon solar cell manufacturing
Authors: Lipiński M. , Kaminski A. , Lelièvre J.‐F. , Lemiti M. , Fourmond E. , Zięba P. 
Published: March 2007

AbstractAn optimization of SiOxNy anti‐reflective coatings with graded index layers for silicon solar cells based on the Bruggeman's effective medium approximation is presented. For simulation of reflectance and absorption of graded layer, the experimental optical data of silicon nitride SiNx:H and oxynitride SiOxNy obtained by Low Frequency (440 kHz) Plasma Enhanced Chemical Vapour Deposition (LF‐PECVD) were used. We have shown that the graded index oxynitride antireflection coating can reduce the effective reflectance to about 2.5% but the high absorption due to high extinction coefficient compensates this improvement and reduces the short circuit current (Jsc) of the solar cell. The improvement in the Jsc can be obtained for graded SiNxOy layer with smaller value of refractive index of SiNx (n = 2.2). In this case the graded SiOxNy layer is characterized by an abrupt concentration profile and can be considered as a double antireflection coating SiO2/SiNx. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Evidence of intrinsic silicon nanostructure formation in SiN matrix deposited by various low temperature CVD techniques
Authors: Lelièvre J.‐F. , Rodriguez H. , Fourmond E. , Quoizola S. , De la Torre J. , Sibai A. , Bremond G. , Ribeyron P.‐J. , Loretz J.‐C. , Araujo D. , Lemiti M. 
Published: March 2007

AbstractIn this work, we report the intrinsic formation of silicon nanostructures (ns‐Si) in non‐stoechiometric amorphous hydrogenated silicon nitride (SiNx:H) obtained by different deposition techniques (UltraViolet photo‐assisted Chemical Vapour Deposition and Low‐Frequency Plasma‐Enhanced CVD using two different reactors). No post‐deposition treatment was needed. The obtained layers were characterized by photoluminescence (PL) and photocurrent (PC) spectroscopy, revealing emission/absorption mechanisms dominated by confined excitons within ns‐Si. Transmission electron microscopy (TEM) confirmed the presence of these ns‐Si, in a crystalline form, for SiNx:H layers obtained by both LF‐PECVD reactors. Thus, quantum confinement effect could be identified for every deposition techniques involved, revealing the formation of intrinsic ns‐Si in the amorphous SiN matrix. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Towards medical diagnostic chips with monolithically integrated optics in glass substrates
Authors: Krawczyk S. K. , Mazurczyk R. , Bouchard A. , Vieillard J. , Hannes B. 
Published: March 2007

AbstractOur objective is to develop miniaturised Lab‐on‐a‐Chip (LOC) analysers, for medical diagnostics and for monitoring of the health status of ill persons. The complete system will make use of disposable chip sensors of the size of a credit card and a control unit of the size of a book. The principle of sensors will be based on the determination of the concentration of “protein markers”, which are related to various illnesses. In order to achieve this objective, it is necessary to integrate some optical components in the Chip. In this contribution we describe a successful development of electrophoretic separation LOC with monolithically integrated optics. These optical components are used for the excitation and for the detection of the fluorescence signal from separated bio‐molecules. The developed module can be considered as one of the main building‐block of the completed diagnostic Chip. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Recent improvements of SiC micro‐resonators
Authors: Godignon P. , Placidi M. 
Published: March 2007

AbstractDue to the increasing demand for sensors operating in harsh environment and significant advancements in high quality SiC layers free of stress,‐this material has received a great interest for the fabrication of micro‐ and nano‐electromechanical systems (MEMS and NEMS). Recent developments have allowed the fabrication of many mechanical SiC devices, especially resonator devices, with a simple cantilever or bridge, which are very attractive as transducers for chemical or biological sensors. Cantilevers, bridges and other resonant structures were successfully fabricated. The first results have clearly shown the advantage of SiC compared to Si for many sensors applications. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical and electrical characterization of SiO2 films obtained by atmospheric pressure chemical vapor deposition
Authors: Juárez H. , Díaz T. , Pacio M. , García S. G. , Rosendo E. , Rubin M. , Romero G. , García A. , Morales C. 
Published: March 2007

AbstractSiO2 films by atmospheric pressure chemical vapor deposition (APCVD) process, using tetraethoxysilane (TEOS) and ozone (O3) as reactant were obtained. The films were deposited on silicon substrates at various temperatures 125, 150, 175, 200, 225 and 250 °C Fourier transforms infrared (FTIR) spectroscopy was used to characterize the SiO2 films. Absorbance spectrums show the vibration modes corresponding to SiO2 films. Additional absorption bands due to residual groups were also observed, but they were found to be dependent on the deposition temperature. The observed current flowing through the oxide could be related to these residual groups, mainly to hydroxyl groups. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Current collapse and reliability of III‐N heterostructure field effect transistors
Authors: Koudymov A. , Shur M. S. , Simin G. , Gaska R. 
Published: March 2007

AbstractMeasurements of GaN HFET lifetime as a function of temperature show that different degradation mechanisms are involved at low temperatures (close to room temperature) and high temperatures (above 150 °C). The degradation at low temperatures is linked to the trap generation and can be explained using the current collapse model. At higher tempe‐ ratures, other degradation mechanisms become important or even dominant. The current collapse related degradation can be diminished by using improved device design, which will greatly increase the overall lifetime (up to long lifetimes obtained by extrapolating high temperature data to room temperature). (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Exact state estimation for linear systems with unknown inputs based on hierarchical super‐twisting algorithm
Authors: Bejarano F.J. , Fridman L. , Poznyak A. 
Published: March 2007

AbstractA robust hierarchical observer is designed for linear time invariant systems with unknown bounded inputs under conditions of strong observability, providing exact state estimation. The main condition for designing the state estimator is the, so‐called, strong observability condition. The supertwisting (second‐order sliding mode) algorithm is used in each step of the hierarchy; the continuity of the supertwisting output injection allows to reconstruct a vector formed by some full column rank matrix premultiplied by the state vector, and that vector is obtainedin a finite time and without any sort of filtration. For the case when the unknown inputs are considered as constant uncertain parameters, the continuous version of the least‐square method is developed. Two numerical examples illustrate the efficiency of the suggested technique. Copyright © 2007 John Wiley & Sons, Ltd.
Examining the dynamics of grain size distributions of gravel/sand deposits in the Sandy River, Oregon with a numerical model
Authors: Cui Yantao 
Published: March 2007

AbstractThis paper describes the application of The Unified Gravel‐Sand (TUGS) model for the simulation of the Sandy River, Oregon. TUGS model employs Wilcock and Crowe's (2003) bedload transport equation for simulation of gravel and sand transport, and is capable of simulating the dynamics of bed material grain size distributions, including the fractions of sand in the deposits. The model has been examined with three large‐scale flume experiments and a flushing flow flume experiment with good agreements in bed profiles, gravel characteristic grain sizes and fractions of sand in the deposits. These examinations, along with descriptions of model development, are presented in a manuscript submitted concomitantly elsewhere (Cui, 2007), and this paper expands model examinations to a natural river. Eight runs are conducted with the Sandy River, Oregon as the prototype river, focusing on the responses of bed material grain size distributions under different hydrologic and sediment supply conditions. Simulation with the recorded discharge and the best understanding of sediment supply in the Sandy River produced good agreement in river longitudinal profile. This simulation also produced decreased median grain size and increased sand fraction in the downstream direction that match well with the general observations in the field. Examinations with varied sand supply indicate that bed material sand fractions are positively correlated with sand supply. Examinations with varied water discharge indicate that increased discharge under the same sediment supply conditions results in decreased bed material sand fraction. Examination of a hypothetical backwater effect from the Columbia River indicates that backwater effect results in increases in bed material sand fractions. Simulation of the sedimentation process upstream of a 14‐m tall dam during dam operation produced similar current bed profile and a stratified sediment deposit very similar to those observed in the field. Copyright © 2007 John Wiley & Sons, Ltd.
Views about science — technology — society interactions held by college students in general education physics and sts courses
Authors: Bradford Cristine Schoneweg , Rubba Peter A. , Harkness William L. 
Published: March 2007

AbstractThis study examined whether and to what extent a general education STS and physics courses helped college students build more informed, realistic views about the interactions among science, technology, and society. Two samples took part in the study, one consisting of 138 college students enrolled in a general education STS course, STS 200‐Critical Issues in Science, Technology and Society, and the other comprising 122 college students enrolled in a general education physics course, PHYS 001‐The Science of Physics, at a large eastern land grant university. Pretest and posttest data were collected using 16 multiple‐choice items selected from the 114 items in the Views on Science‐Technology‐Society (VOSTS) item pool. The findings for each of the 16 VOSTS items were treated descriptively. Additionally, a special scoring procedure was devised for the VOSTS items to allow the use of inferential statistics. The STS students moved toward more “realistic” views of STS interactions on a number of VOSTS items and toward more “naive” views on other VOSTS items. The findings supported the value of general education STS courses. However, they also suggested that courses like STS 200 have room for improvement. The PHYS 001 course had almost no impact on students' views of STS interactions. It should not be expected that college general education science courses, such as PHYS 001, will help students develop more adequate, realistic understandings of the STS interactions. © 1995 John Wiley & Sons, Inc.
Using the earth system for integrating the science curriculum
Authors: Mayer Victor J. 
Published: March 2007

AbstractContent and process instruction from the earth sciences has gone unrepresented in the world's science curricula, especially at the secondary level. As a result there is a serious deficiency in public understanding of the planet on which we all live. This lack includes national and international leaders in politics, business, and science. The earth system science effort now engaging the research talent of the earth sciences provides a firm foundation from the sciences for inclusion of earth systems content into the evolving integrated science curricula of this country and others. Implementing integrated science curricula, especially at the secondary level where potential leaders often have their only exposure to science, can help to address these problems. The earth system provides a conceptual theme as opposed to a disciplinary theme for organizing such integrated curricula, absent from prior efforts. The end of the cold war era is resulting in a reexamination of science and the influence it has had on our planet and society. In the future, science and the curricula that teach about science must seriously address the environmental and social problems left in the wake of over 100 years of preparation for military and economic war. The earth systems education effort provides one such approach to the modernization of science curricula. Earth science educators should assume leadership in helping to establish such curricula in this country and around the world. © 1995 John Wiley & Sons. Inc.
Epistemological considerations in teaching introductory physics
Authors: Hammer David 
Published: March 2007

AbstractEpistemological beliefs are beliefs about knowledge and learning. In a physics class, for example, some students might believe learning consists of memorizing facts and formulas provided by the teacher, whereas others might believe it entails applying and modifying their conceptualizations of phenomena. This article explores, in the context of a debate about velocity from the author's high school physics class, how a perspective of students as having epistemological beliefs might influence a teacher's perceptions of students and intentions for instruction. © 1995 John Wiley & Sons, Inc.
The loss of women from science, mathematics, and engineering undergraduate majors: An explanatory account
Authors: Seymour Elaine 
Published: March 2007

AbstractThe reasons for the loss of high ability women from science, mathematics, and engineering undergraduate majors are not well understood. However, investigators have, consistently, found an early loss of confidence in their ability to “do science” among such women. In seeking to explain why the vulnerability of women to leaving science majors greatly exceeds that of men, the author draws upon the findings of a 3‐year, ethnographic study of factors contributing to high undergraduate attrition rates among men and women of different ethnicities on seven campuses of different type. The explanatory focus is upon the consequences of a misfit between the learned expectations of women entering college mathematics and science classes, and those of faculty and male peers, about the purpose and nature of the undergraduate experience in these majors. © 1995 John Wiley & Sons, Inc.