19 resultados para Si-doping


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This thesis proposes a new thinking on the English teacher and their continuing education, leaving the picture emerging of a new professional, who is producing and being produced. From this perspective, I present an analysis of self writing of thirteen student-teachers, teachers on how they position themselves to be discursively constituted as subjects in the context of continuing education. As part of Applied Linguistics, the theory and method that supports the analysis of data are articulate key elements of Foucault notions, namely:The care of the self, seeking their connection with one another and care of and the self writing. In the theoretical notions of these elements are implied notions of others, such as speech, ethics, technology of the self, subject and truth. (Foucault, 1984, 1995, 2004c, 2006), and questioning the ethics of the subject. I propose to examine selected excerpts from the self writings of student teachers with a specialization in Teaching and Learning the English Language, seeking linguistic processes in the material production of subjectivities.In order to analyze the process of subjectivation, I examine the discursive statements of selected cuts, aiming to learn more specifically, the points of identification and fragments of the uniqueness of the teachers, showing how they care for themselves and reflect upon them in building their subjectivity from the technologies of the self, to occupy the position of English Language teachers. The results show that, in the exercise of self writing, the subject falls, and a practice of asceticism, discursively construct her/his subjectivity

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The work, here present, has as its objective to present in a clear and distinct manner the object of study of Michel Foucault in his last years of teaching at the College de France, namely, the care of the self. We present the care of the self in its birth, in its origin, from the character Socrates and its development until the beginning of the Christian age. With a keen eye, we present Foucault with a work of return and rescue of the care of the self to the personal and academic discussions; we propose, from the self care, to the contemporary subject a problematization of their life so that from this questioning he creates for herself ways of life that are coherence, knowledge and care with which he has of must particular, his himself. Passing by the sources that served as the source of study for Foucault to sketch the birth of care of the self, we design the form with which Foucault has dealt with the documents that speak of the care of self. We present Socrates as one who by excellence ensures that the other will give birth to the forms of knowledge and care of the self or, in other words, we present the care of the self socratic-foucauldian as a constant worry of the other to pay attention to ways in which he conducts her life, it creates for themselves ways of being and, therefore, creates ethics of existence. We present, finally, the care of the self as the cause of continuous immanence of modes of subjectivation of the subject that configure themselves in a non-accepting a determined essence, but a continually updated form . The care of the self leads to a single relationship and educator of modes of subjectivation of the subject; he creates, on the dynamics of temporality, ethical ways of living, which are sustained by an internal coherence of the subject with herself; he admits no stationary nature in the training of the subject, always wants a more beautiful work of himself; he is not isolation, he needs and is made with the other. The care of the self is the principle and the telos of battles and conquests of the subject within his temporality and existence

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We have used ab initio calculations to investigate the electronic structure of SiGe based nanocrystals (NC s). This work is divided in three parts. In the first one, we focus the excitonic properties of Si(core)/Ge(shell) and Ge(core)/Si(shell) nanocrystals. We also estimate the changes induced by the effect of strain the electronic structure. We show that Ge/Si (Si/Ge) NC s exhibits type II confinement in the conduction (valence) band. The estimated potential barriers for electrons and holes are 0.16 eV (0.34 eV) and 0.64 eV (0.62 eV) for Si/Ge (Ge/Si) NC s. In contradiction to the expected long recombination lifetimes in type II systems, we found that the recombination lifetime of Ge/Si NC s (τR = 13.39μs) is more than one order of magnitude faster than in Si/Ge NC s (τR = 191.84μs). In the second part, we investigate alloyed Si1−xGex NC s in which Ge atoms are randomly positioned. We show that the optical gaps and electron-hole binding energies decrease linearly with x, while the exciton exchange energy increases with x due to the increase of the spatial extent of the electron and hole wave functions. This also increases the electron-hole wave functions overlap, leading to recombination lifetimes that are very sensitive to the Ge content. Finally, we investigate the radiative transitions in Pand B-doped Si nanocrystals. Our NC sizes range between 1.4 and 1.8 nm of diameters. Using a three-levels model, we show that the radiative lifetimes and oscillator strengths of the transitions between the conduction and the impurity bands, as well as the transitions between the impurity and the valence bands are strongly affected by the impurity position. On the other hand, the direct conduction-to-valence band decay is practically unchanged due to the presence of the impurity

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In this work we present a study of structural, electronic and optical properties, at ambient conditions, of CaSiO3, CaGeO3 and CaSnO3 crystals, all of them a member of Ca-perovskite class. To each one, we have performed density functional theory ab initio calculations within LDA and GGA approximations of the structural parameters, geometry optimization, unit cell volume, density, angles and interatomic length, band structure, carriers effective masses, total and partial density of states, dielectric function, refractive index, optical absorption, reflectivity, optical conductivity and loss function. A result comparative procedure was done between LDA and GGA calculations, a exception to CaSiO3 where only LDA calculation was performed, due high computational cost that its low symmetry crystalline structure imposed. The Ca-perovskite bibliography have shown the absence of electronic structure calculations about this materials, justifying the present work