Tania Denise Miskinis Salgado

Effects of the surface deposition of nitrogen on the thermal oxidation of silicon in O2

Nitrogen was deposited on the surface layers of Si(100) by ion implantation at a very low energy (approximately 20 eV), at fluences between 1 and 10×1014 cm−2. The samples were thermally oxidized in dry O2 at 1050 °C, and the areal densities and profiles of N and O were determined by nuclear reaction analysis and narrow nuclear resonance profiling, evidencing that: (i) the retained amounts of N just after ion beam deposition stayed in the range between 0.3 and 7×1014 cm−2; (ii) the oxide growth is influenced strongly by the presence of nitrogen, the thickness of the oxide films (which remained between 4 and 30 nm) decreased with the increase of the areal density of nitrogen; (iii) N is partially removed from the system as oxidation proceeds. These observations are discussed in terms of current models for the thermal growth of silicon oxide in the presence of N.

Atomic transport across the interfaces during the formation of ultrathin silicon oxide/nitride/oxide films

The redistribution of O and N during the final, thermal oxidation in dry O2 step in the formation of ultrathin silicon oxide/nitride/oxide dielectric films (ONO) was investigated using isotopic tracing and depth profiling with nanometer resolution. The results show that the final oxidation step induces atomic transport of O and N species in the system, such that the formed ONO structures are not stacked layer structures, but rather a silicon oxynitride ultrathin film, having moderate concentrations of N in the near-surface and near-interface regions, and a high N concentration in the bulk.The redistribution of O and N during the final, thermal oxidation in dry O2 step in the formation of ultrathin silicon oxide/nitride/oxide dielectric films (ONO) was investigated using isotopic tracing and depth profiling with nanometer resolution. The results show that the final oxidation step induces atomic transport of O and N species in the system, such that the formed ONO structures are not stacked layer structures, but rather a silicon oxynitride ultrathin film, having moderate concentrations of N in the near-surface and near-interface regions, and a high N concentration in the bulk.

Effects of the Final Oxidation Step on N and O Distributions in Silicon Oxide/Nitride/Oxide Ultrathin Films

Isotopic tracing was used to determine the distribution of O and N after the final fabrication step of ultrathin silicon oxide/nitride/oxide (ONO) films, revealing how the processing parameters affect the characteristics of the resulting structure. ONO films were prepared on precleaned Si wafers in three steps: (i) thermal oxidation in dry 16 O 2 , at 1000°C in a rapid thermal processing furnace; (ii) remote plasma enhanced chemical vapor deposition of a nitride layer in a mixture of 15 N 2 and silane, and (iii) a second thermal oxidation step in a Joule-effect heated furnace, in dry 18 O 2 , at three different temperatures and for three different times. Nuclear reaction analysis and narrow nuclear resonance depth profiling with nanometric resolution were used to determine the distribution of 16 O, 18 O, and 15 N in the samples, before and after the reoxidation step. It is shown that the final structure is not a stacked one, but rather a silicon oxynitride ultrathin film with variable composition, presenting moderate concentrations of N in the near-surface and near-interface regions, and a higher N concentration in the bulk. Long treatments at high temperatures produce a significant loss and redistribution of N.

Isotopic substitution of N, O, and Si in the thermal oxidation of nitrogen-deposited silicon

Nitrogen was deposited on the surface of Si(100) wafers by ion implantation at a very low energy (approximately 20 eV), at fluences between 1 and 10×1014 cm−2. The samples were thermally oxidized in dry O2 at temperatures between 800 and 1050 °C. Atomic transport of the chemical species involved in the process was investigated by isotopic tracing of N, O, and Si, using depth profiling with nanometric resolution. The obtained results indicate that: (i) the nitrogen atoms deposited on the Si surface are redistributed during thermal oxidation in O2 within the silicon oxide (oxynitride) film, with maxima at the near-surface and near-interface regions; (ii) during growth, O is fixed not only in the near-interface and near-surface regions like in the thermal growth of SiO2 films on Si, but also in the bulk of the growing oxide (oxynitride) film; and (iii) Si is immobile during the thermal oxidation process. The observed modifications in the mechanisms of thermal growth of SiO2 (SiOxNy) films on Si due to the pr...

Visitando, pesquisando, aprendendo e brincando: uma revisão de atividades para o ensino informal de ciências

O trabalho apresenta uma revisao acerca do papel do ensino informal em ciencias. Dentre as discussoes, esta a diferenciacao entre o ensino formal e o informal no que se refere a aprendizagem. Entre os resultados das pesquisas analisadas, destaca-se o fato de que os espacos de educacao nao formal sao importantes complementos a escola. Verificou-se que as estrategias adotadas concebem estes espacos, museus e tambem escolas, como uns locais de interacao efetiva entre alunos, professores e monitores. O objetivo destas atividades, em geral, e a demonstracao ou a simulacao de fenomenos cientificos. Finalmente, parece que as pesquisas em educacao em ciencias sobre ensino formal e informal buscam a compreensao de como as aprendizagens acontecem fora da escola com a intencao de construir um referencial teorico para essas praticas e processos de educacao.

Memória, aprendizagem, emoções e inteligência

Este artigo apresenta uma revisao sobre memoria com conceitos para os seus diferentes tipos e relaciona memoria e cognicao, mostrando a sua importância no desenvolvimento da aprendizagem e da inteligencia. Ao apresentar os diversos tipos de memoria, e mostrado como elas estao relacionadas entre si, tanto no processamento do que deve ser armazenado, como no que deve ser descartado, e quais fatores que influenciam esse processamento. Um paralelo e feito entre as influencias das emocoes na forma como as memorias sao adquiridas, armazenadas e resgatadas. E tambem mostrado como a teoria Cattel-Horn-Carrol das capacidades cognitivas pode ser utilizada para promover o aprimoramento da memoria e, consequentemente, a inteligencia e os processos de aprendizagem. Discute-se, ainda, a importância de se estimular precocemente habilidades cognitivas da pessoa, comecando no nascimento e continuando ao longo de sua vida.

Estudo de Caso: uma proposta para abordagem de funções da Química Orgânica no Ensino Médio

Este trabalho consiste na analise de uma experiencia de aplicacao do metodo de Estudo de Caso a uma turma de segundo ano do Ensino Medio de uma escola publica de Porto Alegre, como forma de abordagem das funcoes da quimica orgânica por meio do tema “Medicamentos”. O objetivo desta proposta e desenvolver uma pratica pedagogica que contribua para que o aluno tenha compreensao do conhecimento cientifico e perceba sua vinculacao com a realidade que o cerca, facilitando dessa forma o aprendizado de conceitos quimicos e favorecendo o fortalecimento de habilidades que possam instrumenta-lo para a tomada de decisao e o exercicio da cidadania. Foram utilizados instrumentos de coleta de dados, antes e depois da realizacao das atividades, numa perspectiva metodologica de pesquisa qualitativa e quantitativa. Os resultados mostram que a estrategia didatica de Estudo de Caso favoreceu aprendizagens conceituais, desenvolvimento de habilidades e motivou os estudantes a se envolveram nas atividades propostas nas aulas de quimica. Palavras-chave: Estudo de Caso, ensino de funcoes orgânicas, desenvolvimento de habilidades.

A utilização da Ciência Forense e da Investigação Criminal como estratégia didática na compreensão de conceitos científicos

AbstrAct (the use of Forensic science and criminal Investigation as a teaching strategy in the understanding of scientific concepts) In this paper we present a brief introduction to the area of Forensic Science and Criminal Investigation, as well as its importance in elucidating crimes. Furthermore, we propose as examples four didactic modules of experimental character (fingerprints, footprints, blood and ballistic), which may promote understanding of phenomena/concepts involved in areas of chemistry, physics and mathematics, and/or can be used in the development of a teaching proposal in the attempt to unravel a fictitious crime in a contextualized and interdisciplinary form. The teacher or responsible for the activity will fit the role of seeking the best way to use these materials within the context of their classes, and the opportunity to discuss with other teachers in order to exchange experiences and thus perceive other forms of application. Keywords: forensic sciences, interdisciplinarity, experiential tasks