Covid-19 and the Return of the State in Africa

Abstract: As African countries battled the Covid-19 crisis in 2020, one of the questions that were raised was whether the state was taking a central stage in the affairs of society, especially solutions to major problems. The question was triggered by the fact that there has been a decline in the capacity, role and prestige of the state in Africa for decades. Yet it seems that the responses to Covid-19, following the WHO guidelines, have placed the state at the centre, without dislocating other stakeholders like the private sector and the civil society. This paper uses the evidence from a select number of African countries of different sizes in various regions of the continent to provide an empirical perspective on the role of the state in Covid-19 responses in 2020 to answer the question of whether Covid-19 has occasioned a return of the state, thus reversing the neoliberal designs in favour of a lean and mean state in Africa

Calculation of C 1s core-level shifts in poly(ethylene terephthalate) and comparison with x-ray photoelectron spectroscopy

Using a first-principle approach, we investigate the C 1s core-level shifts of poly(ethylene terephthalate). The geometrical structure of the polymer is first fully relaxed, then the C 1s core-level shifts are obtained using an approach that includes core-hole relaxation. We compute shifts without geometry relaxation of the excited system, as well as with this relaxation, and find that one of the relative core-level shifts is affected by as much as 0.7 eV by this choice. We compare our ab initio core-level shifts with experimental x-ray photoelectron spectroscopy measurements

Damage reduction and sealing of low-k films by combined He and NH3 plasma treatment

Modification of chemical vapor deposition low-k films upon sequential exposure to helium plasma and then ammonia plasma is characterized using various methods. The He plasma emits extreme ultraviolet (EUV) photons creating O-2 vacancies, which impacts surface reactive sites and induces localized chemical modifications in the first surface monolayers. The subsequent NH3 plasma treatment provides complete sealing of the low-k surface. The depth of the modification, which is a factor of merit of the sealing process, is limited because of the high absorption coefficient of silica-based low-k materials in the range of EUV emission. (C) 2007 The Electrochemical Society.status: publishe

Static Sims Investigation of Metal-polymer Interfaces

The formation of the interface between thermally evaporated metals (aluminium, copper) and polymers [poly(ethylene terephthalate) (PET), poly(methyl methacrylate) (PMMA)] has been investigated by static SIMS. Two generations of instrument have been used. The first one, using a quadrupole mass spectrometer directly connected to the same ultrahigh vacuum environment as the metallization chamber, has allowed an in situ characterization of the interface formation after each metal deposition in the submonolayer regime. The second system, using a time-of-flight (ToF) mass spectrometer, has allowed ex situ analyses of Al/PET, Cu/PET, Al/PMMA and Cu/PMMA interfaces. The high mass resolution of the ToF spectrometer led to the unambiguous identification of the molecular fragments that are characteristic of polymer-metal interaction. The results show that Al atoms react with the oxygenated parts of PET and PMMA. This interaction limits the lateral diffusion of Al atoms on the polymer surface and, consequently, induces a two-dimensional growth of the Al film on these polymer substrates. In the Cu deposition case, a weaker metal-polymer interaction is observed. This leads to Cu clustering and a three-dimensional growth. Time-of-flight SIMS molecular imaging clearly reveals Cu clusters on the PMMA surface

Polymer metallization: Low energy ion beam surface modification to improve adhesion

The interface formation between copper and poly(ethylene terephthalate) (PET) and poly(methyl methacrylate) (PMMA) films is studied in situ by Ion Scattering Spectrometry (ISS). Very low metal fluxes(similar to 10(13) atoms/cm(2) s) and hence low deposition rates are obtained by using a Knudsen's effusion cell. This allows to reach very low metal coverages down to the sub-monolayer regime. The results indicate that without surface activation, Cu atoms interact only very weakly with both polymer surfaces. Indeed, the oxygen/carbon ISS intensify ratio remains nearly unaffected by the metal deposition, showing no preferential shadowing effect. Moreover, the ISS polymer signals are still detected after exposure to Cu atom fluences corresponding to several monolayers coverage. Cu diffusion below the polymer surface is evidenced by the presence of an inelastic multiple collision contribution in the ISS spectra. It is observed that 2 keV He-3(+) ion beam irradiation prior to metallization induces a drastic modification in the interface formation. Ion beam irradiation prevents the metal diffusion into the polymer bulk and leads to an increase of the metal concentration at the surface. In order to explain these results, the surface modifications produced by the ion beam on pristine polymers are studied by ISS and ToF-SIMS. Dehydrogenation and preferential loss of O containing fragments are found. These modifications are associated with the production of radicals leading to the creation of new adsorption sites for the Cu atoms. II is proposed that the reaction between radicals of different macrochains induces a surface crosslinking, that can prevent the diffusion for the deposited metal atoms into the polymer bulk

Interface characterization of nanoscale laminate structures on dense dielectric substrates by x-ray reflectivity

On nanoscale laminate structures, the interface cannot be identified any longer as the separation between two films of bulk materials. The formation of the interface defines the final composition and structure of the laminate structure. As such, the characterization of the interface becomes an important challenge. In this work the nanoscale laminate structures were formed by atomic layer deposition (ALD) of tungsten nitride carbide and tantalum nitride thin films on dense dielectrics [silicon carbide and silicon oxide (SiO2)]. The laminates were studied using x-ray reflectivity. The starting substrate surface is a primary factor in determining the density of the ALD layer. Moreover, in some cases, electron-density perturbations are observed in the vicinity of the interfacial region. A characterization strategy, using a density contrast layer between the silicon substrate and the SiO2 dielectric is presented. Depending on the chemical nature of precursors and substrate, ALD processes can either form specific interfacial organization or induce dielectric modifications, in any case, leading to unexpected metal-dielectric interactions. (C) 2005 American Institute of Physics

Characterization of atomic layer deposited nanoscale structure on dense dielectric substrates by X-ray reflectivity

Interfaces play a crucial role in determining the ultimate properties of nanoscale structures. However, the characterization of such structures is difficult, as the interface can no longer be defined as the separation between two materials. The high sensitivity of electron density to surface and interface reactions has attracted increasing interest in application of X-ray reflectivity (XRR) as probing technique. In this study, the nanolaminate structures were formed by atomic layer deposition (ALD) of tungsten nitride carbide (WNC) and tantalum nitride (TaN) thin films on silicon carbide (SiC), silicon oxide (SiO2) and silicon oxynitride (SiON) substrates and subsequently characterized by XRR. The goal is to establish a relationship between surface chemistry, interface properties and density of the final structure. To achieve this objective, the density variations at the interfaces between ALD TaN and ALD WNC with SiC, SiO2 and SiON films will be quantified by modeling analysis of XRR reflection spectra. From these modeled electron density profiles, specific mechanisms leading to surface dependent structural behavior are proposed

Minimizing Plasma Damage and in situ Sealing of Ultra Low-k Dielectric Films by using Oxygen Free Fluorocarbon Plasmas

Ultralow-k nanocrystalline silica films with an open porosity of 30–31% and a pore radius of 0.8–0.9 nm have been etched using oxygen free highly polymerizing fluorocarbon plasma. It is shown that such plasma allows minimization of plasma damage in comparison with standard oxygen containing CF4 based plasmas and provides in situ sealing of the pores by deposition of fluorocarbon polymers in the film. We also demonstrate that the resulting surface is well suited for the nucleation and growth of atomic layer deposited WCN films. Characterization of the etched low-kdielectric by various analytical instrumentations demonstrates feasibility of this approach for integration of ultralow-kdielectric films