¿Sueña la juventud vulnerable con trabajos precarios? la toma de decisiones en los itinerarios de (In/Ex)clusión educativa

Este trabajo aborda el análisis de los discursos de jóvenes que han tenido dificultades en su itinerario educativo y que han participado en 'itinerarios de segunda oportunidad'. A partir de entrevistas a jóvenes, pretendemos aproximarnos a los argumentos desde los que dan sentido a sus itinerarios académicos y a las decisiones a las que se han enfrentado. Estos argumentos muestran fuertes implicaciones de la posición social de los actores, y están influidos por agentes de la institución educativa y familiar. En ese marco los jóvenes van configurando unas expectativas de futuro. Estas expectativas se debaten entre tres vías: salidas a espacios laborales poco cualificados y precarios, aunque funcionales al sistema productivo; salidas a entornos protegidos con una elevada dependencia; o salidas a vías marginales que les devuelven a redes de proximidad de alta vulnerabilidad. Estos itinerarios evidencian la tensión entre la reproducción social y la resistencia. This work analyses young people's discourses characterized by problematic educational tracks, and who have been part of "second opportunity itineraries". Based on interviews to the young, we try to understand the arguments they use to make sense of their own academic itineraries and the key decisions they have taken in this process. Their arguments highly relate with the actor's social position, and are influenced by agents such as the family and the educational institution. Within this framework, youngsters construct expectations for the future. These expectations follow three different paths: low-qualified and precarious work arenas, which remain functional in the productive system's context; protected settings with high dependency levels; and marginal paths which takes them to proximity networks with high vulnerability. These tracks show the tension between social reproduction and resistance

Atomic structure of Ge quantum dots on the Si(001) surface

In situ morphological investigation of the {105} faceted Ge islands on the Si(001) surface (hut clusters) have been carried out using an ultra high vacuum instrument integrating a high resolution scanning tunnelling microscope and a molecular beam epitaxy vessel. Both species of hut clusters--pyramids and wedges--were found to have the same structure of the {105} facets which was visualized. Structures of vertexes of the pyramidal clusters and ridges of the wedge-shaped clusters were revealed as well and found to be different. This allowed us to propose a crystallographic model of the {105} facets as well as models of the atomic structure of both species of the hut clusters. An inference is made that transitions between the cluster shapes are impossible.Comment: 6 pages, 6 figures. Accepted to JETP Letters (publication date 2010-03-25

Do Vulnerable Youth Dream Of Precarious Employment? Decision Making at (In/Ex) clusion Pathways

Este trabajo aborda el análisis de los discursos de jóvenes que han tenido dificultades en su itinerario educativo y que han participado en “itinerarios de segunda oportunidad”. A partir de entrevistas a jóvenes, pretendemos aproximarnos a los argumentos desde los que dan sentido a sus itinerarios académicos y a las decisiones a las que se han enfrentado. Estos argumentos muestran fuertes implicaciones de la posición social de los actores, y están influidos por agentes de la institución educativa y familiar. En ese marco los jóvenes van configurando unas expectativas de futuro. Estas expectativas se debaten entre tres vías: salidas a espacios laborales poco cualificados y precarios, aunque funcionales al sistema productivo; salidas a entornos protegidos con una elevada dependencia; o salidas a vías marginales que les devuelven a redes de proximidad de alta vulnerabilidad. Estos itinerarios evidencian la tensión entre la reproducción social y la resistencia.This work analyses young people’s discourses characterized by problematic educational tracks, and who have been part of “second opportunity itineraries”. Based on interviews to the young, we try to understand the arguments they use to make sense of their own academic itineraries and the key decisions they have taken in this process. Their arguments highly relate with the actor’s social position, and are influenced by agents such as the family and the educational institution. Within this framework, youngsters construct expectations for the future. These expectations follow three different paths: low-qualified and precarious work arenas, which remain functional in the productive system’s context; protected settings with high dependency levels; and marginal paths which takes them to proximity networks with high vulnerability. These tracks show the tension between social reproduction and resistance.Grupo FORCE (HUM-386). Departamento de Didáctica y Organización Escolar de la Universidad de Granad

Reflectance anisotropy spectroscopy assessment of the MOVPE nucleation of GaInP on Germanium (100)

This work summarizes the observations made on the variation and time evolution of the reflectanceanisotropy signal during the MOVPE growth of GaInPnucleation layers on Germanium substrates. This in situ monitoring tool is used to assess the impact of different nucleation routines and reactor conditions on the quality of the layers grown. This comparison is carried out by establishing a correlation between reflectanceanisotropy signature at 2.1 eV and the morphology of the epilayers evaluated by atomic force microscopy (AFM). This paper outlines the potential of reflectanceanisotropy to predict, explore, and therefore optimize, the best growth conditions that lead to a high quality III–V epilayer on a Ge substrat

Lateral Ordering of InAs Quantum Dots on Cross-hatch Patterned GaInP

We report the use of partially relaxed tensile as well as compressively strained GaInP layers for lateral ordering of InAs quantum dots with the aid of misfit dislocation networks. The strained layers and the InAs QDs were characterized by means of atomic force microscopy, scanning electron microscopy, and X-ray reciprocal space mapping. The QD-ordering properties of compressive GaInP are found to be very similar with respect to the use of compressive GaInAs, while a significantly stronger ordering of QDs was observed on tensile GaInP. Furthermore, we observed a change of the major type of dislocation in GaInP layers as the growth temperature was modified

Generating and measuring the anisotropic elastic behaviour of Co thin films with oriented surface nano-strings on micro-cantilevers

In this research, the elastic behaviour of two Co thin films simultaneously deposited in an off-normal angle method was studied. Towards this end, two Si micro-cantilevers were simultaneously coated using pulsed laser deposition at an oblique angle, creating a Co nano-string surface morphology with a predetermined orientation. The selected position of each micro-cantilever during the coating process created longitudinal or transverse nano-strings. The anisotropic elastic behaviour of these Co films was determined by measuring the changes that took place in the resonant frequency of each micro-cantilever after this process of creating differently oriented plasma coatings had been completed. This differential procedure allowed us to determine the difference between the Young's modulus of the different films based on the different direction of the nano-strings. This difference was determined to be, at least, the 20% of the Young's modulus of the bulk Co

Ge quantum dot arrays grown by ultrahigh vacuum molecular beam epitaxy on the Si(001) surface: nucleation, morphology and CMOS compatibility

Issues of morphology, nucleation and growth of Ge cluster arrays deposited by ultrahigh vacuum molecular beam epitaxy on the Si(001) surface are considered. Difference in nucleation of quantum dots during Ge deposition at low (<600 deg C) and high (>600 deg. C) temperatures is studied by high resolution scanning tunneling microscopy. The atomic models of growth of both species of Ge huts---pyramids and wedges---are proposed. The growth cycle of Ge QD arrays at low temperatures is explored. A problem of lowering of the array formation temperature is discussed with the focus on CMOS compatibility of the entire process; a special attention is paid upon approaches to reduction of treatment temperature during the Si(001) surface pre-growth cleaning, which is at once a key and the highest-temperature phase of the Ge/Si(001) quantum dot dense array formation process. The temperature of the Si clean surface preparation, the final high-temperature step of which is, as a rule, carried out directly in the MBE chamber just before the structure deposition, determines the compatibility of formation process of Ge-QD-array based devices with the CMOS manufacturing cycle. Silicon surface hydrogenation at the final stage of its wet chemical etching during the preliminary cleaning is proposed as a possible way of efficient reduction of the Si wafer pre-growth annealing temperature.Comment: 30 pages, 11 figure

STM and RHEED study of the Si(001)-c(8x8) surface

The Si(001) surface deoxidized by short annealing at T~925C in the ultrahigh vacuum molecular beam epitaxy chamber has been in situ investigated by high resolution scanning tunnelling microscopy (STM) and reflected high energy electron diffraction (RHEED). RHEED patterns corresponding to (2x1) and (4x4) structures were observed during sample treatment. The (4x4) reconstruction arose at T<600C after annealing. The reconstruction was observed to be reversible: the (4x4) structure turned into the (2x1) one at T>600C, the (4x4) structure appeared again at recurring cooling. The c(8x8) reconstruction was revealed by STM at room temperature on the same samples. A fraction of the surface area covered by the c(8x8) structure decreased as the sample cooling rate was reduced. The (2x1) structure was observed on the surface free of the c(8x8) one. The c(8x8) structure has been evidenced to manifest itself as the (4x4) one in the RHEED patterns. A model of the c(8x8) structure formation has been built on the basis of the STM data. Origin of the high-order structure on the Si(001) surface and its connection with the epinucleation phenomenon are discussed.Comment: 26 pages, 12 figure

Morphology Analysis of Si Island Arrays on Si(001)

The formation of nanometer-scale islands is an important issue for bottom-up-based schemes in novel electronic, optoelectronic and magnetoelectronic devices technology. In this work, we present a detailed atomic force microscopy analysis of Si island arrays grown by molecular beam epitaxy. Recent reports have shown that self-assembled distributions of fourfold pyramid-like islands develop in 5-nm thick Si layers grown at substrate temperatures of 650 and 750°C on HF-prepared Si(001) substrates. Looking for wielding control and understanding the phenomena involved in this surface nanostructuring, we develop and apply a formalism that allows for processing large area AFM topographic images in a shot, obtaining surface orientation maps with specific information on facets population. The procedure reveals some noticeable features of these Si island arrays, e.g. a clear anisotropy of the in-plane local slope distributions. Total island volume analysis also indicates mass transport from the substrate surface to the 3D islands, a process presumably related to the presence of trenches around some of the pyramids. Results are discussed within the framework of similar island arrays in homoepitaxial and heteroepitaxial semiconductor systems