Nanoimaging of Organic Charge Retention Effects: Implications for Nonvolatile Memory, Neuromorphic Computing, and High Dielectric Breakdown Devices

While a large variety of organic and molecular materials have been found to exhibit charge memory effects, the underlying mechanism is not well-understood, which hinders rational device design. Here, we study the charge retention mechanism of a nanoscale memory system, an organic monolayer on a silicon substrate, with Au nanoparticles on top serving as the electrical contact. Combining scanning probe imaging/manipulation and density functional simulations, we observe stable charge retention effects in the system and attributed it to polaron effects at the amine functional groups. Our findings can pave the way for applications in nonvolatile memory, neuromorphic computing, and high dielectric breakdown devices

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

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

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

Enhanced initial growth of atomic-layer-deposited metal oxides on hydrogen-terminated silicon

A route is presented for activation of hydrogen-terminated Si(100) prior to atomic layer deposition. It is based on our discovery from in situ infrared spectroscopy that organometallic precursors can effectively initiate oxide growth. Narrow nuclear resonance profiling and Rutherford backscattering spectrometry show that surface functionalization by pre-exposure to 108 Langmuir trimethylaluminum at 300 °C leads to enhanced nucleation and to nearly linear growth kinetics of the high-permittivity gate dielectrics aluminum oxide and hafnium oxide

Size, Shape, and Crystallinity of Luminescent Structures in Oxidized Si Nanoclusters and H-Passivated Porous Si

Near-edge and extended x-ray absorption fine structure measurements from a wide variety of H-passivated porous Si samples and oxidized Si nanocrystals, combined with electron microscopy, ir-absorption, {alpha}-recoil, and luminescence emission data, provide a consistent structural picture of the species responsible for the luminescence observed in these systems. For luminescent porous Si samples peaking in the visible region, i. e., {le}700nm, their mass-weighted-average structures are determined here to be particles - not wires, whose short-range character is crystalline - not amorphous, and whose dimensions - typically <15 {angstrom} - are significantly smaller than previously reported or proposed. These results depend only on sample luminescence behavior, not on sample preparation details, and thus have general implications in describing the mechanism responsible for visible luminescence in porous silicon. New results are also presented which demonstrate that the observed luminescence is unrelated to either the photo-oxidized Si species in porous Si or the interfacial suboxide species in the Si nanocrystals

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]

Anthracological evidence suggests naturalness of Pinus pinaster in inland southwestern Iberia

The study of well-preserved archaeological charcoals in the pre-Roman Iron Age settlement of Castillejos II (Badajoz, Spain) is used to reconstruct environmental conditions and land-use practices in vegetation landscapes in the southwest of the Iberian Peninsula before the arrival of Roman civilization. The results support that, while evergreen Quercus forests dominated during the Holocene, Pinus pinaster existed as a natural element of southwestern Iberian Peninsula vegetation. Although its presence could be linked to anthropogenic disturbance or fire history, it is suggested that P. pinaster populations survived during the Holocene in the region, mixed with oaks or in monospecific stands in mountain enclaves. This hypothesis contrasts with previous assumptions that P. pinaster was not autochthonous in the area

Evidence and Policy in Aid-Dependent Settings

This chapter examines how the political dynamics of aid relationships can affect the use of evidence within health policymaking. Empirical examples from Cambodia, Ethiopia and Ghana illustrate how relationships between national governments and donor agencies influence the ways in which evidence is generated, selected, or utilised to inform policymaking. We particularly consider how relationships with donors influence the underlying systems and processes of evidence use. We find a number of issues affecting which bodies or forms of evidence are taken to be policy relevant, including: levels of local technical capacity to utilise or synthesise evidence; differing stakeholder framing of issues; and the influence of non-state actors on sector-wide systems of agenda setting. The chapter also reflects on some of the key governance implications of these arrangements in which global actors promote forms of evidence use – often under a banner of technical efficiency – with limited consideration for local representation or accountability