Real-time, in situ monitoring of surface reactions during plasma passivation of GaAs

Real-time, in situ observations of surface chemistry during the remote plasma passivation of GaAs is reported herein. Using attenuated total reflection Fourier transform infrared spectroscopy, the relative concentrations of -As-O, -As-H, -H2O, and -CH2 bonds are measured as a function of exposure to the effluent from a microwave discharge through NH3, ND3, H2, and D2. The photoluminescence intensity (PL) from the GaAs substrate is monitored simultaneously and used qualitatively to estimate the extent of surface state reduction. It was found that, while the -CHx(x = 2,3) and -As-O concentrations are reduced rapidly, the rates at which the -As-H concentration and the PL intensity increase are relatively slow. The concentration of -H2O on the GaAs surface increases throughout the process as surface arsenic oxides and the silica reactor walls are reduced by atomic hydrogen. These observations suggest that removal of elemental As by reaction with H at the GaAs–oxide interface limits the passivation rate

Africa: Modernity without Development?

Events in Africa over the last two decades have puzzled many. Worsening poverty, corruption, as well as the repeated occurrence of coups or extreme civil violence, all conspire to give a cheerless, if not downright frightening, image of the continent. Are the causes of this crisis to be found in Africa's place in the world economy or in the continual disorder which afflicts the continent? Is the present turmoil a temporary setback or has it become a permanent condition? Why is there such breakdown of society? Will the present efforts for democratization ensure an improvement in the living conditions of the vast majority or merely benefit the elites? Has the continent been 'left behind by the rest of the world', as some have argued? Taken together, these issues raise the more general question of modernization

‘Because it’s our culture!’ (Re)negotiating the meaning of lobola in Southern African secondary schools

Payment of bridewealth or lobola is a significant element of marriage among the Basotho of Lesotho and the Shona of Zimbabwe. However, the functions and meanings attached to the practice are constantly changing. In order to gauge the interpretations attached to lobola by young people today, this paper analyses a series of focus group discussions conducted among senior students at two rural secondary schools. It compares the interpretations attached by the students to the practice of lobola with academic interpretations (both historical and contemporary). Among young people the meanings and functions of lobola are hotly contested, but differ markedly from those set out in the academic literature. While many students see lobola as a valued part of ‘African culture’, most also view it as a financial transaction which necessarily disadvantages women. The paper then seeks to explain the young people’s interpretations by reference to discourses of ‘equal rights’ and ‘culture’ prevalent in secondary schools. Young people make use of these discourses in (re)negotiating the meaning of lobola, but the limitations of the discourses restrict the interpretations of lobola available to them

Navigating ‘taxation’ on the Congo River: the interplay of legitimation and ‘officialisation’

Based on comprehensive research among boat operators and navy personnel working on the Congo River (DRC), this article explores how assessments of ‘taxation’ are shaped by the interplay of legitimation and ‘officialisation’. As such, it draws upon and contributes to scholarly debates on taxpayers’ attitudes towards taxation. While boat operators resent having to pay a plethora of authorities, including the navy, along the Congo River, the article demonstrates how they locate these ‘taxes’ on a spectrum from more to less legitimate. These assessments are shaped by various factors: authorities’ legitimacy as ‘measured’ by their official mandate and importance; public and non-official service provision; and the deployment of symbols of ‘stateness’. In interaction, these factors legitimise and ‘officialise’ ‘taxes’ by the navy that are prohibited in legislation. These findings caution against the a priori use of the labels ‘official’ and ‘non-official’, emphasising the need to better grasp these notions’ emic understandings

Diffusion of In0.53Ga0.47As elements through hafnium oxide during post deposition annealing

Diffusion of indium through HfO2 after post deposition annealing in N-2 or forming gas environments is observed in HfO2/In0.53Ga0.47As stacks by low energy ion scattering and X-ray photo electron spectroscopy and found to be consistent with changes in interface layer thickness observed by transmission electron microscopy. Prior to post processing, arsenic oxide is detected at the surface of atomic layer deposition-grown HfO2 and is desorbed upon annealing at 350 degrees C. Reduction of the interfacial layer thickness and potential densification of HfO2, resulting from indium diffusion upon annealing, is confirmed by an increase in capacitance. (C) 2014 AIP Publishing LLC

Thermal stability of amorphous LaScO3 films on silicon

The thermal stability of amorphous LaScO3 thin films deposited by molecular-beam deposition directly on (001) Si was investigated by high-resolution transmission electron microscopy (HRTEM), transmission infrared absorption spectroscopy (IRAS), and x-ray diffraction (XRD). IRAS indicated that the as-deposited films contained < 0.1 A of SiO2 at the interface between LaScO3 and silicon. XRD studies showed that the films remained amorphous after annealing in N-2 at 700 degrees C, although HRTEM showed structural order on an similar to 1 nm length scale even in the as-deposited films. By 800 degrees C, the LaScO3 had started to crystallize and formed a similar to 5 nm thick Sc-deficient interlayer between it and silicon. (c) 2006 American Institute of Physics

Ab initio optical properties of Si(100)

We compute the linear optical properties of different reconstructions of the clean and hydrogenated Si(100) surface within DFT-LDA, using norm-conserving pseudopotentials. The equilibrium atomic geometries of the surfaces, determined from self-consistent total energy calculations within the Car-Parrinello scheme, strongly influence Reflectance Anisotropy Spectra (RAS), showing differences between the p(2x2) and c(4x2)reconstructions. The Differential Reflectivity spectrum for the c(4x2) reconstruction shows a positive peak at energies < 1 eV, in agreement with experimental results.Comment: fig. 2 correcte

Interwoven migration narratives: identity and social representations in the Lusophone world

First published online: 17 Oct 2016This article provides an exploratory analysis of the life narratives of migrants in the Portuguese-speaking world. By interweaving the life experiences of eight participants in three thematic clusters – ‘shared past’, language and sense of community – we propose a critique of the deep-seated idea of the Lusophone space as a community constructed by the harmonious conviviality of different countries and people. Drawing on contributions from cultural studies, social psychology, anthropology and sociology, we first aim to give voice to the human subjects who embark on migrations and then to understand how the engendered process of identity construction is framed by their social world, simultaneously reframing it. Thus, we aim at shedding light on the ways in which aspects of the political discourses on Lusophony are used (and are instrumental) to the migrants’ identity narrative (re)construction.This work was supported by Fundacao para a Ciencia e a Tecnologia: [Grant Number PTDC/CCI-COM/105100/2008]