Structural and optical properties of compensated microcrystalline silicon films

Boron-doped microcrystalline silicon films were deposited in a plasma enhanced chemical vapor deposition (PECVD) system using silane (SiH4) diluted in hydrogen, and diborane (B2H6) as a dopant gas. The effects of the Boron concentration on the optical and structural properties were investigated by the constant-photocurrent method (CPM) and atomic force microscopy (AFM) measurements. The variations in the optical constants (refractive index, absorption coefficient and optical gap) as a function of wavelength were carried out from the optical transmission and CPM spectra. By increasing the doping level, a systematic increase in the absorption coefficient spectra in the low-energy region between 0.7 - 1.2 eV was observed. It was found that the increase of Boron concentration in the samples results in changes of the grain size. Correlations between optical properties and the density of states (DOS) were also studied.Fil: Dussan, A.. Universidad Nacional de Colombia; ColombiaFil: Koropecki, Roberto Roman. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Arce, Roberto Delio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Schmidt, Javier Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin

Interplay of disorder and interaction in Majorana quantum wires

We study the interplay between disorder and interaction in one-dimensional topological superconductors which carry localized Majorana zero-energy states. Using Abelian bosonization and the perturbative renormalization group (RG) approach, we obtain the RG-flow and the associated scaling dimensions of the parameters and identify the critical points of the low-energy theory. We predict a quantum phase transition from a topological superconducting phase to a non-topological localized phase, and obtain the phase boundary between these two phases as a function of the electron-electron interaction and the disorder strength in the nanowire. Based on an instanton analysis which incorporates the effect of disorder, we also identify a large regime of stability of the Majorana-carrying topological phase in the parameter space of the model.Comment: New version includes a section and an appendix with a detailed study on the effect of interaction and disorder on the stability of Majorana end-states. 6 pages, 1 figur

A variational model of fracture for tearing brittle thin sheets

Tearing of brittle thin elastic sheets, possibly adhered to a substrate, involves a rich interplay between nonlinear elasticity, geometry, adhesion, and fracture mechanics. In addition to its intrinsic and practical interest, tearing of thin sheets has helped elucidate fundamental aspects of fracture mechanics including the mechanism of crack path selection. A wealth of experimental observations in different experimental setups is available, which has been often rationalized with insightful yet simplified theoretical models based on energetic considerations. In contrast, no computational method has addressed tearing in brittle thin elastic sheets. Here, motivated by the variational nature of simplified models that successfully explain crack paths in tearing sheets, we present a variational phase-field model of fracture coupled to a nonlinear Koiter thin shell model including stretching and bending. We show that this general yet straightforward approach is able to reproduce the observed phenomenology, including spiral or power-law crack paths in free standing films, or converging/diverging cracks in thin films adhered to negatively/positively curved surfaces, a scenario not amenable to simple models. Turning to more quantitative experiments on thin sheets adhered to planar surfaces, our simulations allow us to examine the boundaries of existing theories and suggest that homogeneous damage induced by moving folds is responsible for a systematic discrepancy between theory and experiments. Thus, our computational approach to tearing provides a new tool to understand these complex processes involving fracture, geometric nonlinearity and delamination, complementing experiments and simplified theories.Fil: Li, Bin. Universidad Politécnica de Catalunya; España. Sorbonne Université; Francia. Centre National de la Recherche Scientifique; FranciaFil: Millán, Raúl Daniel. Universidad Nacional de Cuyo. Facultad de Ciencias Aplicadas a la Industria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentina. Universidad Politécnica de Catalunya; EspañaFil: Torres Sánchez, Alejandro. Universidad Politécnica de Catalunya; EspañaFil: Roman, Benoît. Centre National de la Recherche Scientifique; Francia. Sorbonne Université; FranciaFil: Arroyo Balaguer, Marino. Universidad Politécnica de Catalunya; Españ

La traducción de autores franceses de ciencias sociales y humanidades en la Argentina. Estado y perspectivas actuales de una presencia invariante

De los tres polos que dominan la edición de lengua española, España, México y Argentina, la producción argentina ha desempeñado y continúa desempeñando un papel central como introductora de autores franceses de ciencias sociales y humanas en esta geografía editorial. En tal sentido, este trabajo indaga la dinámica de este segmento de la actividad editorial entre 1990 y 2011, a partir del relevamiento y análisis cuantitativo de los autores y títulos traducidos, y de la aproximación cualitativa a los sellos, mediadores y traductores que posibilitaron esta circulación.Of the three centers that dominate the Spanish language book publishing geography, Spain, Mexico and Argentina, the Argentine production has played and continues to play a central role as introducer of French authors of social and human sciences in this publishing geography. In this sense, this article addresses the dynamics of this area of the editorial activity between 1990 and 2011, from the survey and quantitative analysis of translated authors and titles, and the qualitative approach to the publishing houses, mediators and translators that allowed this circulation.Fil: Dujovne, Miguel Alejandro. Instituto de Desarrollo Económico y Social; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Parque Centenario. Centro de Investigaciones Sociales; ArgentinaFil: Ostroviesky, Heber Roman. Universidad Nacional de General Sarmiento. Instituto del Desarrollo Humano; ArgentinaFil: Sora, Gustavo Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Instituto de Antropología de Córdoba; Argentin

MPI-CUDA parallel linear solvers for block-tridiagonal matrices in the context of SLEPc's eigensolvers

[EN] We consider the computation of a few eigenpairs of a generalized eigenvalue problem Ax = lambda Bx with block-tridiagonal matrices, not necessarily symmetric, in the context of Krylov methods. In this kind of computation, it is often necessary to solve a linear system of equations in each iteration of the eigensolver, for instance when B is not the identity matrix or when computing interior eigenvalues with the shift-and-invert spectral transformation. In this work, we aim to compare different direct linear solvers that can exploit the block-tridiagonal structure. Block cyclic reduction and the Spike algorithm are considered. A parallel implementation based on MPI is developed in the context of the SLEPc library. The use of GPU devices to accelerate local computations shows to be competitive for large block sizes.This work was supported by Agencia Estatal de Investigacion (AEI) under grant TIN2016-75985-P, which includes European Commission ERDF funds. Alejandro Lamas Davina was supported by the Spanish Ministry of Education, Culture and Sport through a grant with reference FPU13-06655.Lamas Daviña, A.; Roman, JE. (2018). MPI-CUDA parallel linear solvers for block-tridiagonal matrices in the context of SLEPc's eigensolvers. Parallel Computing. 74:118-135. https://doi.org/10.1016/j.parco.2017.11.006S1181357

Density of States in Thin Boron-Doped Microcrystalline Silicon Films Estimated from the Thermally Stimulated Conductivity Method

In this work, a series of boron-doped microcrystalline silicon samples [μc-Si:H(B)] were deposited by plasma-enhanced chemical vapor deposition, using silane (SiH4) diluted in hydrogen, and diborane (B2H6) as a dopant gas. The concentration of B2H6 in SiH4 was varied in the range of 0-100 ppm. The density of states was obtained from the thermally stimulated conductivity technique and compared with results obtained by the modulated photoconductivity methods. To explain the poor agreement between the density of states obtained from the thermally stimulated conductivity and the other methods, it is shown by means of numerical simulations that the density of states is very sensitive to experimental errors introduced in the calculation of the μn τn product (mobility of electron × lifetime of the electron). The thermally stimulated conductivity method is applied here for the first time to calculate the density of defect states in the forbidden band of μc-Si:H samples.Fil: Dussan, A.. Universidad Nacional de Colombia. Departamento de Física; ColombiaFil: Schmidt, Javier Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Física del Litoral; ArgentinaFil: Koropecki, Roberto Roman. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Física del Litoral; Argentin

Obtención de Películas Delgadas de Silicio Policristalino a partir de Clorosilanos en Reactores de CVD

En este trabajo se presentan resultados obtenidos en la deposición y caracterización estructural de láminas delgadas de silicio policristalino. Como método de deposición se usó el CVD térmico a partir de triclorosilano, y como sustrato un vidrio comercial de alta temperatura. Se logró la deposición de películas policristalinas, con tamaños de grano entre 0,2 y 0,5 micrones, a temperaturas de entre 730 y 840 ºC. Las muestras presentan un crecimiento tipo columnar y una clara orientación cristalina (2 2 0). Estas características serían propicias para el transporte electrónico en la dirección perpendicular al sustrato.In this work, results obtained from the deposition and structural characterization of polycrystalline silicon thin films are presented. Thermal CVD from trichlorosilane was used as deposition method, and a high temperature commercial glass was used as substrate. The deposition of polycrystalline films with grain sizes between 0.2 and 0.5 microns was achieved, at temperatures in the range of 730 to 840 ºC. The samples present a columnar type growth and a clear (2 2 0) crystal orientation. This characteristics would be suitable for the electronic transport in the direction perpendicular to the substrate.Fil: Benvenuto, Ariel Gastón. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); ArgentinaFil: Schmidt, Javier Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); ArgentinaFil: Buitrago, Roman Horacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentin

Correlación de modelos de transporte de VRH para muestras de silicio microcristalino dopadas con Boro

En este trabajo se realizaron medidas de conductividad en un amplio rango de temperaturas (120 300K), presenta un comportamiento térmicamente activado con una única energía de activación que cambia con el grado de compensación. Para la región de bajas temperaturas se encontró que el transporte de portadores es controlado por Hopping de Rango Variable (VRH), con excepción de la muestra con concentración de Boro más baja. Se presenta un método desarrollado denominado Modelo Difusional que permite calcular los parámetros de hopping y correlacionarlos con los obtenidos a partir de la teoría de percolación, obteniendo a su vez un factor numérico que los corrige.The temperature dependence of dark conductivity has been measured over a wide temperature range (120 300K), the carrier transport was found to be thermally activated with a single activation energy, which changed with the compensation degree. In the low temperature region, Variable Range Hopping (VRH) was established as a predominant electronic transport mechanism with the exception for the lowest concentration of Boron. We present a model called “Diffusional” from which the hopping parameters were obtained and compared with the parameters calculated from the percolation theory. A numerical correlation factor of the hopping parameters was also calculated.Fil: Dussan Cuenca, Anderson. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Buitrago, Roman Horacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Schmidt, Javier Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin