bluuebunny/crossref_metadata_2025 huggingface dataset:
Acurácia do diâmetro de ponta de cones de gutapercha com diferentes conicidades
Authors: Castilho Eloísa Higashi , Britto Maria Leticia Borges , Machado Manoel Eduardo de Lima , Nabeshima Cleber Keiti
Published: December 2022

Objetivo: O objetivo deste estudo foi analisar o diâmetro da ponta de cones de guta-percha com diferentes conicidades, considerando a especificação do fabricante. Materiais e Métodos: Cento e quarenta cones de guta percha (Dentsply Maillefer): F2, F3, e 25, 30, 35 e 40 de conicidade .02, .04 e .06 (n = 10) foram utilizados neste estudo. Os cones foram presos em uma régua calibradora, e observados em microscópio ótico com aumento de 40x. Então, o diâmetro da ponta de cada cone foi medido com paquímetro digital. Os dadosforam categorizados como corretos ou incorretos utilizando margem de erro de ±0,01 mm e submetidos ao teste Exato de Fisher (p ≤ 0,05). Resultados: Somente 4 cones de guta percha estavam incorretos, porém não houve diferença estatisticamente significativa entre os cones em relação ao padrão estabelecido pelo fabricante. Conclusão: Conclui-se que os cones principais da marca Dentsply Maillefer, independente de sua conicidade (.02, .04, .06, F2 e F3), possuem o diâmetro da ponta calibrado de acordo com a especificação do fabricante.Descritores: Guta-percha. Obturação do canal radicular. Endodontia.
Perfil dos orientadores de bolsistas de Iniciação Científica da Faculdade de Odontologia da Universidade Federal de Minas Gerais
Authors: Freitas Gabrielle Amaral , Zarzar Patrícia Maria Pereira de Araúo , Paiva Saul Martins , Pordeus Isabela Almeida , Ferreira Fernanda Morais
Published: December 2022

O objetivo desse estudo foi traçar o perfil dos orientadores de Iniciação científica da Faculdade de odontologia da Universidade Federal de Minas Gerais durante uma década. Foi feita uma avaliação retrospectiva da formação, da carreira e da experiência de orientações na pós-graduação e na graduação dos professores da instituição que orientaram alunos como bolsistas do Programa de Iniciação científica de 2006 a 2016, com base em informações dos currículos cadastrados na plataforma Lattes do CNPq. A produção intelectual dos docentes foi analisada (quanti e qualitativamente, Qualis 2015). Para avaliar a correlação entre o número de orientações de Iniciação cientifica e as demais variáveis numéricas, foi usado o coeficiente de correlação de Spearman. Para verificar se existia diferença entre o número de orientações de Iniciação cientifíca entre as categorias das variáveis categóricas, foram usados os testes de Mann-Whitney e Kruskal-Wallis. Pouco mais de 38% (n=44) do total de professores da Instituição, com formações, tempo de titulação e níveis de carreira diversos, alocados nos 4 departamentos, orientaram bolsistas no período; dos quais 18 tinham orientações em andamento. Quase 90% destes apresentam vínculo com Programa de pós-graduação. As áreas responsáveis pelo maior número de bolsas vigentes são a Odontopediatria e Odontologia social e preventivas. O número de orientações de iniciação científica concluídas e em andamento por orientador apresentou correlação positiva e significante (rs, p<0,05) com a produção científica qualificada (≥ B3) e com o número de orientações de pós-graduação stricto sensu, mas não esteve correlacionada a outras produções e orientações. Embora o perfil de orientadores de iniciação científica entre o período de 2006-2016 tenha sido diversificado, é possível identificar algumas particularidades e, sobretudo, detectar que a participação no Programa é pequena diante do total de docentes com titulação e capacidade de orientação e do número de alunos da Instituição. 

 

Descritores: Academias e Institutos. Educação Superior. Pesquisa em Odontologia. Pesquisadores.
Acesso aos serviços de saúde bucal em Campina Grande/Paraíba: um estudo de série temporal
Authors: Bezerra de Lima Thaynná Barboza , Sobreira Duarte Bezerra Lígia Natália , Ferreira Amorim Heloísa Raquel , Wanderley Gomes Freire Déborah Ellen , Rocha Madruga Renata Cardoso
Published: December 2022

Introdução: Este estudo avaliou o acesso aos serviços odontológicos em áreas cobertas pela Estratégia Saúde da Família em Campina Grande – PB, comparando as séries temporais dos anos de 2009 e 2014.

Materiais e Métodos: Tratou-se de um estudo quantitativo, analítico, com desenho do tipo transversal, de base populacional, do seguimento de dois estudos, com dados primários coletados prospectivamente, longitudinal ou de seguimento. A análise dos dados foi realizada através do SPSS 18.0, em duas etapas: uma descritiva e outra analítica. Na primeira foram feitas as distribuições de frequência das variáveis quantitativas, na segunda foram testadas as associações, utilizando-se o Qui quadrado de Pearson. Para todas as análises foi considerado significante o nível de 5%.

Resultados: Os fatores sócio-bio-demográficos associados ao acesso no estudo de 2009, foram: idade, estado civil, renda do respondente e escolaridade. Em 2014, além desses, esteve associada à renda familiar.

Conclusão: Pôde-se concluir que a equidade não está sendo respeitada. Este estudo pretende dar uma contribuição para a lacuna existente na avaliação de tais serviços.

Palavras-Chave: Estratégia Saúde da Família. Serviços de Saúde Bucal. Acesso aos serviços de Saúde.
Propriedades físico-químicas de cimentos endodônticos à base de óxido de zinco e eugenol
Authors: Alves de Santana Castro Gabriela , Silva Morais Malena Ana , Monteiro Falcão Carlos Alberto , Reinaldo Lima Luciana , Arêa Leão Ferraz Maria Ângela
Published: December 2022

Objetivo: Analisar as propriedades físico-químicas, escoamento, tempo de presa, solubilidade e alteração dimensional, dos cimentos endodônticos à base de óxido de zinco e eugenol: Endomethasone N, Endofill e Grosmann, de acordo com a especificação número 57 da American Dental Association.

Métodos: Realizou-se os testes nas condições ambientais de 23° ± 2°C e 50 ± 5% de umidade relativa do ar, mantidas 48 h antes dos procedimentos, repetindo-se cinco vezes e obtendo-se uma média aritmética.

Resultados: Os cimentos à base de óxido de zinco e eugenol analisados apresentaram tempo de endurecimento elevados, para o teste de escoamento, o Endofill e Grossman apresentaram-se acima do estabelecido. Em relação à solubilidade, o Endomethasone N esteve dentro do padrão e os demais cimentos excederam.

Conclusão: Todos os cimentos analisados obtiveram valores diferentes do recomendado para alteração dimensional. Nenhum dos cimentos enquadrou-se completamente nas normatizações.

Descritores: Odontologia. Propriedades físicas e químicas. Pesquisa em odontologia.
Hospitalização para casos de câncer de boca e faringe no Brasil
Authors: Lucas Brum Moreira da Silva Thalita , Alexandra Alves Waneska , De Paula Lopes Rosado Lucas , Ketrine Lustosa Souza Brisa , Nascimento de Aquino Sibele
Published: December 2022

Objetivo: Avaliar a internação hospitalar por câncer de boca e faringe no Brasil no período de 2008 a 2017.

Métodos: Estudo das internações por estas neoplasias registradas no Sistema de Informação Hospitalar disponíveis no DATASUS/MS entre 2008 e 2017.

Resultados: Foram registradas 263.556 mil internações por câncer de boca e faringe. O Sudeste apresentou a maior frequência de casos (44,3%). A maior taxa de internação ocorreu no Sul (19,6/100 mil habitantes). As maiores taxas de letalidade encontradas foram no Norte (12,7%) e Sudeste (12,3%). Houve um predomínio de internações em regime privado (53,5%) e em caráter de urgência no Brasil (53,5%). A média de permanência hospitalar foi de 6,4 dias. A taxa de letalidade em caráter de urgência foi maior do que em caráter eletivo. A taxa de internação apresentou tendência decrescente e a taxa de letalidade hospitalar, tendência de incremento de 0,2% a cada ano. A análise de índice de desenvolvimento humano médio e taxa de internação mostrou correlação moderada positiva entre essas variáveis e as regiões do país. Houve maior custo médio em reais por internação hospitalar em caráter eletivo e a região Centro-Oeste obteve maior média de custo financeiro (por guia autorizada) nesta modalidade.

Conclusão: Observa-se um elevado número de internações por estes tipos de câncer no Brasil, além de um acentuado custo e alta média de permanência hospitalar, sendo variável entre as regiões do país.

Descritores: Neoplasias bucais. Hospitalização. Mortalidade.
Comparação entre alinhadores ortodônticos e aparelhos ortodônticos fixos convencionais:
Authors: Couto Bárbara Linhares Brazil , Abreu Lucas Guimarães
Published: December 2022

Objetivo: O objetivo dessa revisão sistemática e meta-análise foi comparar a eficácia e a eficiência dos alinhadores ortodônticos (AO) com os aparelhos ortodônticos fixos convencionais (AOFC).
Métodos: Foram realizadas buscas no PubMed, Scopus, Web of Science e Google Scholar. As referências recuperadas nas buscas foram avaliadas por dois autores. Aquelas que atenderam aos critérios de elegibilidade foram incluídas. A avaliação da qualidade dos estudos foi feita com a ferramenta Cochrane. Uma meta-análise foi realizada. As buscas nas bases de dados recuperaram 997 referências. Após a remoção das duplicatas, 859 referências foram avaliadas e 14 estudos foram incluídos.
Resultados: As meta-análises demonstraram que os AOFC foram mais eficazes que os AO para corrigirem discrepâncias oclusais (diferença de média = 3,32). Não houve diferenças entre os dispositivos com relação a dor nos primeiros dias de tratamento (diferença de média = 0,25). Os AOFC apresentaram maior eficácia na correção de parâmetros relacionados à avaliação do sorriso. Os AOFC também foram relacionados à uma maior dificuldade ao comer, maior duração da primeira consulta e do tratamento e um maior número de consultas de urgência (p < 0,05). Indivíduos usando AO apresentaram melhores parâmetros de saúde gengival à curto prazo, mais relatos de dor a longo prazo e demandaram maior tempo do ortodontista nas consultas (p < 0,05). Os principais problemas metodológicos apresentados pelos estudos incluídos foram na sequência da geração aleatória, alocução oculta e cegamento dos participantes/pessoal.
Conclusão: Conclui-se que os AOFC foram mais eficazes para correção da má oclusão, apesar de exigirem um maior tempo de tratamento e estarem associados a dificuldades ao comer.
Descritores: Aparelhos ortodônticos fixos. Aparelhos ortodônticos removíveis. Má oclusão. Eficiência. Eficácia. Índice periodontal.
Magazyny energii niezbędnym elementem transformacji energetycznej
Authors: Adamska Barbara
Published: December 2022

Zgodnie z polskim prawodawstwem magazyny energii stanowią pełnoprawny element rynku elektroenergetycznego. Obowiązujące regulacje są jednak niewystarczające i nie przekładają się na modele biznesowe będące podstawą do inwestycji w magazyny w różnych segmentach rynku: prosumenckim, przemysłowym i komercyjnym oraz wielkoskalowym. W artykule przedstawiono obecne uregulowania europejskie i polskie dotyczące magazynów energii oraz usługi, jakie magazyny mogą świadczyć na potrzeby systemu elektroenergetycznego. Wskazano również na potrzebę porozumienia sektorowego na rzecz rozwoju magazynowania energii w Polsce w celu stworzenia warunków do rozwoju krajowej branży gospodarczej.
The Power of Partnership in Open Government
Authors: Piotrowski Suzanne J. , Berliner Daniel , Ingrams Alex
Published: December 2022

What the Open Government Partnership tells us about how international initiatives can and do shape domestic public sector reform.

At the 2011 meeting of the UN General Assembly, the governments of eight nations—Brazil, Indonesia, Mexico, Norway, Philippines, South Africa, the United Kingdom, and the United States—launched the Open Government Partnership, a multilateral initiative aimed at promoting transparency, empowering citizens, fighting corruption, and harnessing new technologies to strengthen governance. At the time, many were concerned that the Open Government Partnership would end up toothless, offering only lip service to vague ideals and misguided cyber-optimism. The Power of Partnership in Open Government offers a close look, and a surprising affirmation, of the Open Government Partnership as an example of a successful transnational multistakeholder initiative that has indeed impacted policy and helped to produce progressive reform.

By 2019 the Open Government Partnership had grown to 78 member countries and 20 subnational governments. Through a variety of methods—document analysis, interviews, process tracing, and quantitative analysis of secondary data—Suzanne J. Piotrowski, Daniel Berliner, and Alex Ingrams chart the Open Government Partnership's effectiveness and evaluate what this reveals about the potential of international reform initiatives in general. Their work calls upon scholars and policymakers to reconsider the role of international institutions and, in doing so, to differentiate between direct and indirect pathways to transnational impact on domestic policy. The more nuanced and complex processes of the indirect pathway, they suggest, have considerable but often overlooked potential to shape policy norms and models, alter resources and opportunities, and forge new linkages and coalitions—in short, to drive the substantial changes that inspire initiatives like the Open Government Partnership.

This book will be available in an open access format to coincide with the print publication date.
Copyright's Broken Promise
Authors: Willinsky John
Published: December 2022

A comprehensive proposal for reforming copyright law to ensure sustainable public access to research and scholarship.

Open access is widely supported by researchers, librarians, scholarly societies, and research funders, as well as large and small publishers. Yet despite this support—and the pandemic's demonstration of the importance of open access for scientific progress—the scholarly publishing market is failing to deliver open access quickly enough. In Copyright's Broken Promise, John Willinsky presents the case for reforming copyright law so that it supports, rather than impedes, public access to research and scholarship. He draws on the legal strategy of statutory licensing to set out the terms and structures by which the Copyright Act could ensure that publishers are fairly compensated for providing immediate open access.

What sets Willinsky's analysis apart is its focus on the current state of scholarly publishing. Because copyright offers so little legal support for moving publishing to open access despite the benefit for science, he says it is time to stop regarding the Copyright Act as a law of nature that can only be circumvented, contravened, or temporarily set aside. Specifically, he proposes that the Copyright Act add a new category of work, called “research publications,” which would be subject to statutory licensing. This would allow publishers to receive royalty payments from the principal institutional users (universities, industry R&D, research institutes, and so on) and sponsors of the work (foundations and government agencies), while providing immediate open access.
Effect of Storage Period with Different Packaging Materials on Physico Chemical Parameters and Shelf Life of Osmotically Dehydrated Pineapple Cubes (Ananas comosus. var. Queen)
Authors: Manasa B. , Mishra R. Purnima , Joshi Veena , Vijaya D.
Published: December 2022

The present study was carried out to determine the suitable packaging material for osmo dehydrated pineapple product and also to assess quality of the product during storage. Pineapple slices were steam blanched for 2 min, followed by immersion in osmotic solution containing sucrose syrup of three concentrations i.e of 50°Brix, 60ºBrix and 70°Brix in combination with 0.1% KMS + 0.3% citric acid + 0.1 % sodium benzoate followed by drying in two methods i.e. cabinet tray drying and hot air oven drying at 60ºC until the moisture content of the product attained equilibrium. The physico-chemical properties and evaluated for the four months of storage period. During storage period, moisture%, reducing sugars and pH showed an increasing trend while other parameters like TSS ºBrix, non-reducing sugars %, total sugars%, acidity%, ascorbic acid%, organoleptic properties showed a decreasing trend. Among the packaging materials, osmo-dehydrated pineapple cubes packed in Aluminum laminated polyethylene of 200 gauge stored at ambient temperature were found to be the best followed by high density polyethylene packaging of 200 gauge in retaining various attributes like minimal moisture gain, better retention of TSS ºBrix, acidity%, ascorbic acid% and organoleptic properties when compared to the other packaging material during the four months storage period.
Smart Meter Data based Load Analysis Using Clustering Technique
Authors: Sapna P. Fathima , Singh Dr.R. Lal Raja
Published: December 2022

In this study, clustering is investigated as a method for improving energy efficiency based on smart meters for a number of household applications that are both currently available and expected to become available in the near future. These applications include smart thermostats, smart lights, smart water heaters, smart washing machines, and smart refrigerators. We describe a novel approach to load balanced clustering that is founded on the K-means Clustering algorithm. Our algorithm's major goal is to optimize network lifetime while maintaining acceptable sensing coverage in scenarios in which sensor nodes generate either uniform or non-uniform data traffic. This can be accomplished by maintaining acceptable sensing coverage. We also provide a new clustering cost function that takes into consideration not only the volume of traffic but also the amount of work that is required to communicate across substantial geographic distances. This is done so that we can achieve this objective. We demonstrate that our algorithm is able to improve both load analysis as well as load balancing in the domestic area by running extensive simulations that compare the proposed algorithm to leading state-of-the-art clustering approaches and then comparing the results to one another. This allows us to demonstrate that our algorithm is able to improve both load analysis as well as load balancing in the domestic area. In addition to this, it demonstrates the culmination of a stage in the processing of a dataset in order to compute the typical quantity of energy load that is utilized by consumers.
Time-resolved waveguide modulation of a conjugated polymer
Authors: Sinclair M. , McBranch D. , Moses D. , Heeger A. J.
Published: July 2002

We present a new pump and probe technique for measuring intensity-dependent refractive indices (n2) of waveguide quality thin films, and we apply it to films of polydiacetylene-(CH2)4OCONHOCOC4H9 (PDA-4BCMU). Just below the exciton absorption band, the real part of n2 is negative with magnitude ≊10−7(MW/cm2)−1. The initial fast response of n2 is followed by a slower (∼2.5 ps) decay, in close agreement with the decay of the bleaching of the exciton absorption following resonant excitation. These results are consistent with phase space filling by excitons as the mechanism for the nonlinear index.
Strain dependence of p-i-n hydrogenated amorphous silicon junctions
Authors: Utsunomiya Michito , Yoshida Akira
Published: July 2002

The effects of mechanical strain on the electrical properties of p-i-n hydrogenated amorphous silicon junction devices were investigated. When strain was applied parallel to the junction plane, both the forward and reverse currents increased with increasing compressive strain and decreased with increasing tensile strain. The ratio for change in current was 8% under the strain of 7.5×10−4, and the strain sensitivity was as large as that in the piezoresistance effect of crystalline silicon. The strain dependence is due to a change in carrier concentration induced by a displacement of energy band and a change in carrier lifetime.
Measurement of single 14 MeV neutron bursts with 100 ps time resolution
Authors: Kania D. R. , Lane S. M. , Prussin S. G.
Published: July 2002

We have constructed a detector using neutron-damaged GaAs and used it to measure subnanosecond 14 MeV neutron bursts from laser-driven deuterium-tritium filled microspheres. The detector’s very fast response (measured to be 60 ps full width at half-maximum) is due to the phenomenon of radiation-induced conductivity. The absolute sensitivity of the detector has been measured and is in excellent agreement with Monte Carlo calculations. We have also verified that the dectector is linear with neutron flux over two orders of magnitude.
Growth of CdTe-InSb multilayer structures on (100) InSb substrates using molecular beam epitaxy
Authors: Williams G. M. , Whitehouse C. R. , Cullis A. G. , Chew N. G. , Blackmore G. W.
Published: July 2002

Molecular beam epitaxy has been used to grow multilayer structures of CdTe/InSb on (100)InSb substrates. To minimize interdiffusion effects, a particularly low growth temperature was used. This study presents the first transmission electron microscope and secondary-ion mass spectrometer investigations of this multilayer system. The work clearly demonstrates that the multilayers have high structural quality and that there is no large scale interdiffusion of the matrix elements. Roughening is observed at the ‘‘InSb grown on CdTe’’ interface, although only relatively minor undulations are present at the inverted interface. A possible explanation for this effect is described.
Preparation of TiN films by photochemical vapor deposition
Authors: Motojima Seiji , Mizutani Hidetoshi
Published: July 2002

The TiN films have been prepared by photochemical vapor deposition using a D2 lamp from a gas mixture of TiCl4 -NH3 (or N2) -H2. The deposition temperature of the TiN films was lowered by 50–100 °C by irradiation with a D2 lamp as compared to that without irradiation. The deposition rate was increased by 35–300% with irradiation.
Residual acceptor impurities in undoped high-purity InP grown by metalorganic chemical vapor deposition
Authors: Bose S. S. , Szafranek I. , Kim M. H. , Stillman G. E.
Published: July 2002

Zn and an unidentified acceptor species, labeled A1, are the only residual acceptors that have been observed in a wide variety of undoped high-purity InP samples grown by metalorganic chemical vapor deposition. Carbon is not incorporated at detectable concentrations as a residual acceptor in metalorganic chemical vapor deposited InP. However, the longitudinal and transverse optical phonon replicas of the free-exciton recombination occur at the same energy as the donor/conduction band-to-acceptor peaks for C acceptors in low-temperature photoluminescence spectra. Since these replicas are usually present in photoluminescence spectra measured under moderate or high optical excitation, care must be exercised so that these peaks are not misinterpreted as C-related transitions.
Focused ion beam channeling effects and ultimate sizes of GaAlAs/GaAs nanostructures
Authors: Laruelle F. , Bagchi A. , Tsuchiya M. , Merz J. , Petroff P. M.
Published: July 2002

We show that focused ion beam implantation of Ga into GaAlAs/GaAs quantum wells occurs much deeper than expected from theory of implantation into amorphous GaAs and that the lateral straggling is one order of magnitude smaller than predicted by the same theories. We show that channeling is the main mechanism involved in these effects. The small probe size achieved with the focused ion beam is thus preserved 200 nm below the surface.
Enhanced magnetic anisotropy at the percolation threshold of Fe-SiO2 composite thin films
Authors: Holtz R. L. , Lubitz P. , Edelstein A. S.
Published: July 2002

Ferromagnetic resonance (FMR) measurements at 9.6 GHz and room temperature are reported for very thin (50 Å) sputtered films of Fe-SiO2 with volume fractions of Fe, f, spanning the percolation threshold at fc=0.57. It is inferred from the FMR linewidths that the magnetic anisotropy of the percolating composite of Fe particles peaks at fc. Possible mechanisms for this anisotropy enhancement are examined and it is argued that the shape anisotropy of the percolation clusters may be the principal contribution. These results and our interpretations provide a possible explanation for the peak in the coercivity near the percolation threshold of Fe-SiO2 composite films recently reported by S. H. Liou and C. L. Chien [Appl. Phys. Lett. 52, 512 (1988)].
Analytical technique for determining the polarization dependence of optical matrix elements in quantum wires with band-coupling effects
Authors: Sercel Peter C. , Vahala Kerry J.
Published: July 2002

We present an analytical technique for determining polarization-dependent optical transition matrix elements in quantum wires which rigorously incorporates the effects of band coupling. Using this technique, we examine the polarization anisotropy of the two lowest energy optical transitions in a GaAs quantum wire. Contrary to assumptions employed in previous studies, we show that the valence states involved in these transitions are a strong admixture of light and heavy hole character. The lowest energy transition is found to be four times stronger for electric fields oriented parallel to the wire than for the perpendicular orientation. In contrast, the next highest transition does not interact with optical waves polarized along the wire axis. We discuss sources of error which arise in simpler one-band models of this phenomenon in addition to the neglect of band coupling and show that the coupled band model presented here is essential for predicting these effects.
Laser action in the blue-green from optically pumped (Zn,Cd)Se/ZnSe single quantum well structures
Authors: Ding J. , Jeon H. , Nurmikko A. V. , Luo H. , Samarth N. , Furdyna J. K.
Published: July 2002

We have obtained optically pumped laser action in the form (Zn,Cd)Se/ZnSe single quantum well structures prepared by molecular beam epitaxy. Near-room-temperature lasing under pulsed excitation has been achieved and high repetition quasi-continuous mode operation at temperatures so far up to 120 K. Rapid gain switching has generated pulses of approximate 20 ps in duration.
Molecular view of the interfacial adhesion in aluminum-silicon carbide metal-matrix composites
Authors: Rao B. K. , Jena P.
Published: July 2002

The binding energies, electron charge transfer, bond lengths, and core level shifts of Al-Al, Al-Si, Al-C, and Si-C dimers have been calculated self-consistently using the linear combination of atomic orbitals-molecular orbital theory. The exchange interactions are treated using the unrestricted Hartree–Fock theory and correlation corrections are included through the Möller–Plesset perturbation scheme up to fourth order. The results are used to understand the nature and strength of bonding at the interface of Al and SiC crystals. The strong bonding of Al-C dimers compared to Al-Al and Al-Si is shown to be responsible for the aluminum carbide formation at the interface. The charge transfer between the constituent atoms in the dimer and the accompanying core level shifts are also shown to be characteristic of what has been observed at the Al/SiC interface.
Photochemical hole burning of tetraphenylporphin in epoxy resin: Effect of crosslinked structure
Authors: Furusawa Akira , Horie Kazuyuki , Suzuki Taro , Machida Shinjiro , Mita Itaru
Published: July 2002

Photochemical hole burning (PHB) of free-base tetraphenylporphin (TPP) in epoxy resin was performed at 4.2–80 K. Effect of crosslinked structure of the epoxy resin on the dephasing time T2, low-energy excitation modes, and the temperature dependence of Debye–Waller factor were studied through the PHB measurements. The excellent thermal stability of TPP in epoxy resin including the hole burning above liquid-nitrogen temperature (80 K) was demonstrated.
Destruction of a MgF2 optical coating by 250 keV α particle irradiation
Authors: Mendenhall Marcus H. , Weller Robert A.
Published: July 2002

Magnesium fluoride coatings ∼170 Å thick have been evaporated onto mirror-quality Be substrates in ultrahigh vacuum and subsequently subjected to 250 keV α particle irradiation at room temperature. Analysis of the irradiated area by medium energy backscattering spectrometry revealed that the irradiation selectively removed fluorine with an initial yield of 2.2 fluorine atoms per incident α particle. A visible degradation in reflectivity, which became progressively more extensive with increasing dose, was observed after an α particle fluence of 1016 cm−2. After a total irradiation of 4×1017 cm−2 less than 20% of the fluorine in the film remained, effectively reducing it to metallic magnesium. The effect of this change on the reflectivity of the surface was catastrophic.
Stimulated emission via inelastic exciton-exciton scattering in ZnSe epilayers
Authors: Newbury P. R. , Shahzad K. , Cammack D. A.
Published: July 2002

Stimulated emission at 6 K by optical excitation has been investigated in ZnSe epilayers. A detailed examination of the spectra below threshold indicates that the stimulated emission is due to inelastic exciton-exciton scattering, in contrast with some recent reports that lasing is due to electron-hole plasma luminescence modified by self-absorption. A red shift of the lasing line at high pump intensities has also been modeled in terms of the exciton-exciton and band filling mechanisms, giving excellent agreement with the data.
Many-body effects on the linewidth enhancement factor in quantum well lasers
Authors: Chow Weng W. , Koch Stephan W. , Sargent Murray , Ell Claudia
Published: July 2002

A many-body theory that includes band-gap renormalization, plasma screening, and interband Coulomb effects is used to calculate the linewidth enhancement factor α in quantum well lasers. We find significant variations in α with carrier density, suggesting that improvements in the laser linewidth and reduction in filamentation effects are possible for some laser configurations.
Stress in thick diamond films deposited on silicon
Authors: Van Damme Nobuko S. , Nagle Dennis C. , Winzer Stephen R.
Published: July 2002

20-μm-thick diamond films deposited on Si single-crystal substrates by microwave plasma-enhanced chemical vapor deposition showed significant curvature. The internal stress distribution was estimated using the model of an elastic bimetallic strip. The results indicate that the films are under a mean tensile stress of 1.1 GPa, and are discussed using information from x-ray diffraction and Raman spectra.
All optical, high contrast absorptive modulation in an asymmetric Fabry–Perot étalon
Authors: Heffernan J. F. , Moloney M. H. , Hegarty J. , Roberts J. S. , Whitehead M.
Published: July 2002

We report a 27:1 switching contrast ratio with 2.5 mW of power in an asymmetric Fabry–Perot étalon. The modulation is achieved by optical saturation of the excitonic absorption profile of a 95 Å GaAs/AlGaAs multiple quantum well structure grown on a high-reflectivity dielectric stack mirror.
Interferometric characterization of 160 fs far-infrared light pulses
Authors: Greene B. I. , Federici J. F. , Dykaar D. R. , Jones R. R. , Bucksbaum P. H.
Published: July 2002

We report the first interferometric characterization of freely propagating, subpicosecond, far-infrared (FIR) light pulses. FIR light was generated via short pulse photoexcitation of a semi-insulating InP wafer. The half width of the intensity interferogram was 230 fs. The FIR light contained frequency components from 3 to 150 cm−1.
Hydrocarbon reaction with HF-cleaned Si(100) and effects on metal-oxide-semiconductor device quality
Authors: Kasi S. R. , Liehr M. , Thiry P. A. , Dallaporta H. , Offenberg M.
Published: July 2002

The surface reactivity of hydrogen-passivated, HF-cleaned Si(100) towards hydrocarbon adsorption is examined by surface analysis; most hydrocarbons adsorb on the surface. Dangling bonds formed during thermal processing react with fragmented organic molecules forming SiC. Metal-oxide-semiconductor devices fabricated on contaminated surfaces are degraded, with the degree of degradation depending on the nature of the contaminant.
Interface trap generation and electron trapping in fluorinated SiO2
Authors: Vishnubhotla Lakshmanna , Ma T. P. , Tseng Hsing-Huang , Tobin Philip J.
Published: July 2002

Electron trapping and oxide trap generation have been studied in polycrystalline-Si gate metal-oxide-semiconductor (metal-SiO2-Si) capacitors in which F was introduced into the SiO2 layer by implantation into the Si gate followed by a drive-in process. Three key findings are presented: (i) consistent with previous reports, the fluorinated SiO2/Si interface becomes more resistant to ionizing radiation or hot-electron damage; (ii) the incorporation of fluorine introduces electron traps with a small capture cross section of approximately 1×10−18 cm2; and (iii) the presence of F suppresses the generation of new oxide traps under high-field hot-electron injection. Possible explanations are discussed.
Molecular beam epitaxial growth of InAsSb strained layer superlattices. Can nature do it better?
Authors: Ferguson I. T. , Norman A. G. , Joyce B. A. , Seong T-Y. , Booker G. R. , Thomas R. H. , Phillips C. C. , Stradling R. A.
Published: July 2002

Molecular beam epitaxial growth of a normally homogeneous InAs0.5Sb0.5 alloy below 430 °C results in its coherent phase separation into platelets of two different alloy compositions with tetragonally distorted crystal lattices. This produces a ‘‘natural’’ strained layer superlattice (n-SLS) with clearly defined interfaces modulated in the [001] growth direction. A description of the n-SLS growth mode in InAsSb is outlined, and the optical response of a n-SLS structure, which extends to 12.5 μm−considerably further than that of a homogeneous InAs0.5Sb0.5 layer (8.9 μm)−is reported.
Transport properties of epitaxial YBa2Cu3Ox films at step edges
Authors: Friedl G. , Roas B. , Römheld M. , Schultz L. , Jutzi W.
Published: July 2002

To study the current-carrying capability of interconnections between conducting planes in a YBa2Cu3Ox-insulator multilayer system, the transport properties of laser-deposited YBa2Cu3Ox striplines at different step edges in 〈100〉 SrTiO3 substrates were investigated. Step edges with various heights between 100 and 800 nm and slope angles a=2.5°, 10°, 25°, 40°, and 65° were fabricated by Ar+ ion milling. The previous ion milling of one part of the substrate does not affect the crystal growth and the transport properties of the superconductor, which has been checked by electrical and x-ray measurements. Two ways for a high transport current between conducting planes were realized. At flat angles up to 30°, a critical current density of ≳106 A/cm2 at 77 K can be achieved for a step stripline with film thickness d0 smaller than the step height h. If the film thickness d0 is larger than the step height, high superconducting current densities can also be achieved for a≳65°.
Room-temperature Si3N4 and Ge3N4 growths by Si and Ge surface irradiation with a N2 electron cyclotron resonance plasma: An x-ray photoemission study
Authors: Bolmont D. , Bischoff J. L. , Lutz F. , Kubler L.
Published: July 2002

An ultrahigh vacuum compatible electron cyclotron resonance (ECR) plasma source is employed for the first time in studying the surface nitridation with N2 on Si (001)-2×1 at low substrate temperature (Ts=RT). The exposure to the efficiently activated and dissociated nitrogen flux in the microwave plasma is not limited to the silicon surface states but results in the formation of ultrathin dielectric near-stoichiometric Si3N4 layers (∼20 Å) analyzed in situ by x-ray photoelectron spectroscopy (XPS). These films, without hydrogen content and silicon deposit, could easily be grown in few minutes at RT and at relatively low working pressures (∼10−4 mbar in the chamber) without destroying the underlying Si substrate as checked by x-ray photoelectron diffraction (XPD). Composition deviations to the Si3N4 stoichiometry of the grown nitride layers are also discussed in relation with the contamination oxygen content and the contribution of the interface subnitride configurations.
Doping effect of oxygen or nitrogen impurity in hydrogenated amorphous silicon films
Authors: Morimoto Akiharu , Matsumoto Minoru , Yoshita Masahiro , Kumeda Minoru , Shimizu Tatsuo
Published: July 2002

O, N, or C impurity was separately incorporated into a-Si:H films by hot-wall glow discharge decomposition. The effect of the impurity incorporation was investigated by electrical and electron spin resonance measurements. Both O and N impurities were found to increase the dark conductivity by decreasing its activation energy in a-Si:H films. Furthermore, it was found that O and N impurities delay the photoresponse. C impurity, however, has no appreciable effect on them. These findings suggest that O and N impurities shift the Fermi level upward and form a trapping state for photoexcited electrons, supporting our O+3 and N+4 model.
Exact and moment equation modeling of electron transport in submicron structures
Authors: Geurts Bernard J. , Nekovee Maziar , Boots Henk M. J. , Schuurmans Martin F. H.
Published: July 2002

We compare I-V characteristics of a semiconducting submicron n+nn+ diode as predicted by extended moment equation approximations to those obtained from the solution of the corresponding Boltzmann equation. All lower order models fail in the predominantly ballistic regime. Moreover, the conductance is inadequately predicted by these models, even in nonballistic cases due to the high build-in electric fields.
A physical model for boron penetration through an oxynitride gate dielectric prepared by rapid thermal processing in N2O
Authors: Hwang Hyunsang , Ting Wenchi , Kwong Dim-Lee , Lee Jack
Published: July 2002

In this paper a physical model is presented for boron penetration through an oxynitride gate dielectric prepared by rapid thermal processing in a nitrous oxide (N2O) ambient. Compared with a conventional rapid thermally grown oxide, oxynitride dielectrics show excellent diffusion barrier properties to the dopant (BF2). The Auger electron spectroscopy nitrogen depth profile shows nitrogen pileup at the Si/SiO2 interface, which may explain the lower segregation coefficient (≊20 times lower) of the oxynitride dielectric, as expected from suprem-iii simulation with modified diffusivity values.
Ultrafast metal-semiconductor-metal photodiodes fabricated on low-temperature GaAs
Authors: Klingenstein M. , Kuhl J. , Nötzel R. , Ploog K. , Rosenzweig J. , Moglestue C. , Hülsmann A. , Schneider Jo. , Köhler K.
Published: July 2002

GaAs metal-semiconductor-metal photodiodes fabricated on GaAs grown at low substrate temperatures (200 °C) have been investigated in the time domain by electro-optic sampling. It could be shown that these diodes have a faster response, a considerably reduced long time tail, and can be used at larger bias than comparable diodes produced on GaAs grown at 700 °C. Temperature-dependent measurements show that the tail can be described by hopping conductivity and disappears below 50 K.
Si ejection and regrowth during the initial stages of Si(001) oxidation
Authors: Cahill David G. , Avouris Ph.
Published: July 2002

The initial stages of oxidation of the Si(001)-2×1 surface have been studied using scanning tunneling microscopy and spectroscopy. Among the new sites generated by the exposure of this surface to O2 are 1.4 Å high bumps on top of the surface. Upon annealing the O2-exposed surface, or upon O2 exposure at an elevated temperature, these bumps form highly anisotropic islands. Evidence is presented that these bumps and islands are made up of silicon ejected from the surface by the oxidation reaction.
In situ scanning tunneling microscopy observation of surface morphology of GaAs(001) grown by molecular beam epitaxy
Authors: Heller E. J. , Lagally M. G.
Published: July 2002

The surface morphology of molecular-beam-epitaxy-grown GaAs(001) has been investigated using in situ scanning tunneling microscopy and reflection high-energy electron diffraction. Films grown on nominally flat substrates at very slow growth rates display a multilevel system of terraces elongated along [11̄0], suggesting an edge energy anisotropy of the order of 10:1 and a preference for sticking at B-type steps.
Low pressure chemical vapor deposition of oxide from SiH4/O2: Chemistry and effects on electrical properties
Authors: Liehr M. , Cohen S. A.
Published: July 2002

The low pressure chemical vapor deposition (CVD) process of SiO2 from SiH4 and O2 has been analyzed. For deposition at pressures ranging from 10−3 to 3 Torr, with no carrier gas, the process is dominated by fast gas-phase reactions. In situ analytical techniques, such as mass spectrometry and high-resolution electron energy loss spectroscopy, indicate that hydroxyl groups are reaction products and are imbedded into the growing oxide at temperatures from 300 to 600 °C. Presence of these groups is detrimental to the electrical properties of metal-oxide-semiconductor (MOS) structures, e.g., by causing low-field breakdown and by increasing the interface state density. Low-pressure (SiH4/O2) oxides are thus principally not well suited for gate-oxide applications because of their underlying chemistry.
Density of states in the pseudo-gap of amorphous silicon-germanium alloys from electrical and optical measurements
Authors: Pisarkiewicz T. , Kolodziej A. , Schabowska-Osiowska E. , Stapinski T. , Rodzik A. , Rava P.
Published: July 2002

Amorphous hydrogenated silicon-germanium alloys a-Si1−xGex:H in the form of thin films were prepared by rf sputtering and chemical vapor deposition methods with x varying from 0 to 0.63. Optical transmission, reflection, and photoconductivity measurements in the visible and near-infrared regions of light enabled determination of the optical energy gap, band-tail states distribution, and density of defect states near midgap. Dark conductivity and photoconductivity were measured in the temperature range of 300–500 K. Electronic band structure (density of states versus energy) for a-Si0.74Ge0.26:H thin film was derived on the basis of optical measurements, dark conductivity, and photoconductivity.
Optical absorption in plasma-deposited silicon oxynitride films
Authors: Ance C. , de Chelle F. , Ferraton J. P. , Leveque G. , Ordejón P. , Ynduráin Félix
Published: July 2002

We present an experimental and theoretical study of the optical absorption of amorphous silicon oxynitride films. The optical absorption coefficient α in the energy range from 4 to 10 eV has been measured for SiOxNyHz films between the nitride and oxide compositions grown by plasma-enhanced chemical vapor deposition. We have also calculated the coefficient α for SiOxNy alloys assuming a random mixture of Si—N and Si—O bonds within the disordered alloy. The variation of the optical gap Eg with the composition and the appearance of steps in the optical absorption for oxygen-rich samples are discussed.
Preparation of nickel nanoparticles by metalorganic route
Authors: Chatterjee A. , Chakravorty D.
Published: July 2002

Nickel particles of sizes in the range 5–11 nm have been prepared by the decomposition of a suitable metalorganic compound on the surfaces of micrometer-sized potassium bromide crystallites. Infrared absorption spectra of nanocomposites comprising these particles dispersed in potassium bromide matrix have been delineated. Effective medium theory is used to explain the experimental results.
Separation of two distinct fast interface state contributions at the (100)Si/SiO2 interface using the conductance technique
Authors: Uren M. J. , Brunson K. M. , Hodge A. M.
Published: July 2002

We have studied the annealing of fast and slow Si/SiO2 interface states generated by 10-MeV electron irradiation using the conductance technique. The fast-state conductance peak is shown to be separable into contributions from defects characterized by two different capture cross sections, densities of states, and annealing behaviors.
Characterization of epitaxial layers by the depth dependence of boron diffusivity
Authors: van Oostrum K. J. , Zalm P. C. , de Boer W. B. , Gravesteijn D. J. , Maes J. W. F.
Published: July 2002

Differences in boron diffusivity have been used to characterize epitaxially grown silicon layers. After oxidation-enhanced diffusion of boron spikes, a decrease in boron diffusivity with increasing depth is observed in epitaxial silicon layers grown by molecular beam epitaxy and fast gas switching vapor deposition, in contrast to layers grown by low-temperature chemical vapor deposition. The reduced boron diffusivity is thought to be caused by an oversaturation of vacancy defects, acting as interstitial traps, suppressing the diffusion of boron.
Enhancement of Shubnikov–de Haas oscillations by carrier modulation
Authors: Schacham S. E. , Haugland E. J. , Alterovitz S. A.
Published: July 2002

A drastic enhancement of the Shubnikov–de Haas (SdH) pattern is obtained by recording the changes in the quantum oscillations of magnetoresistance due to modulation of the carrier concentration. The technique enables measurement of the SdH waveform at relatively high temperatures and in samples with moderate mobilities. The modulated waveform shows selective enhancement of the low-frequency SdH oscillations associated with the upper subband. Thus, we were able to record very clear oscillations generated by a carrier concentration well below 5×1010 cm−2. The theory for this selective enhancement is provided.
Extremely low resistivity, high electron concentration ZnSe grown by planar-doping method
Authors: Zhu Ziqiang , Mori Hiroshi , Yao Takafumi
Published: July 2002

The n-type ZnSe with electron concentration up to 3×1020 cm−3 and low resistivity down to 1×10−4 Ω cm has been grown using a planar-doping technique of chlorine during molecular beam epitaxy. The photoluminescence evaluation shows that the planar-doped ZnSe layers are superior to uniformly doped ones especially for the case of high Cl doping. The in-depth profile of Cl concentration in a planar-doped sample was measured with a secondary ion mass spectroscopy (SIMS). The SIMS analysis shows only slight diffusion of the incorporated Cl atoms even in highly doped samples.
Nanoscale CoSi2 contact layer growth from deposited Co/Ti multilayers on Si substrates
Authors: Hong Feng , Rozgonyi George A. , Patnaik Bijoy
Published: July 2002

In this letter, we describe procedures for forming continuous, planar, and thermally stable 12-nm-thick CoSi2 layers via Co/Si interaction through an interfacial Ti(O) diffusion barrier layer. Three Co and three Ti layers were deposited sequentially on Si-(100) substrates by dual source thermal evaporation with Ti as the first layer. Oxygen was found to be selectively incorporated into all Ti layers during deposition. Following a 550 °C, 2 h anneal the morphology of the silicide layer depended strongly on the thickness of the initial Ti(O) layer. For an initial Ti(O) layer of ∼5 nm, both Co and Si readily diffused to form a Co silicide interfacial layer with a very rough, faceted interface. Increasing the Ti(O) thickness to ∼10 nm stopped Si out diffusion and reduced Co in diffusion such that a uniform 6 nm CoSix interfacial layer formed. Selective removal of the upper layers and a 750/800 °C annealing produced a 12 nm CoSi2 layer with a resistivity of ∼28 μΩ cm.
Is the exponential tail in amorphous semiconductors caused by random charges?
Authors: Kemp Mathieu , Silver Marvin
Published: July 2002

We discuss an alternative to the current views on the origin of the exponential band tail in amorphous semiconductors. Our model is based on the potential fluctuations due to randomly distributed charges. We show that with random charges, the exponentiality of the band tail is a consequence of the exponential distribution of charged cluster sizes and of the minimal separation between localized states and charged clusters.