196,563 research outputs found
EU Federalism in Crisis
No full textIn the run-up to this week’s European Council, Karel Lannoo offers his assessment of what has been put on the table so far in response to the euro crisis – and what more needs to be done. He starts with an assessment of the measures taken in the ‘six-pack’ and the debate on the Euro-plus Pact and then addresses some operational elements of the European Stability Mechanism and the question whether the EU is, as often alleged, a transfer union. The CEPS Chief Executive concludes his brief by proposing a pragmatic agenda of items on which the EU could advance towards a more federal economic union.
A bit more clarity, please, M. de Larosière. CEPS Commentaries, 3 March 2009
No full textThis Commentary assesses the report by the high-level group on financial supervision, chaired by former IMF Managing Director and Bank of France Governor Jacques de Larosière. The author, CEPS CEO Karel Lannoo, finds that the group’s recommendations offer a useful first step, but that its proposals need to be clarified and simplified, and their implementation accelerated. In his view, the report should lead to a clear roadmap to be adopted by the EU Council and some choices need to be thought through more carefully, procedures more fully specified and structures elaborated. Moreover, he advocates amending the EU Treaty to establish a European System of Financial Supervisors – a question carefully avoided by the report
Capital Adequacy vs. Liquidity Requirements in Banking Supervision in the EU. CEPS Policy Briefs No. 84, 1 October 2005
No full textThe debate on banking supervision over the last decade has largely focused on capital requirements and solvency of financial institutions. The interaction between solvency and liquidity has been much less debated. In this new Policy Brief, CEPS Chief Executive Karel Lannoo and Jean-Pierre Casey, CEPS Research Fellow, discuss the approach to be taken with regard to control of liquidity in the EU. To put the subject into perspective, they first review current developments in financial market liquidity and then discuss the possible impact of the New Basel Accord on the liquidity of financial institutions. The authors further analyse liquidity control in the context of EU financial regulation, and explore whether liquidity control should be harmonised in the EU, and if so, how this could be done
3D real-space quantum transport simulation of nanowire MOS transistors: Influence of the ionized doping impurity
No full textWe report a numerical study of both donor- and acceptor doping impurity effects in the quantum transport of silicon nanowire metal-oxide-semiconcluctor (MOS) transistors. The code is based on a full three-dimensional (3D) real-space non-equilibrium green function (NEGF) formalism self-consistently coupled with the 3D Poisson equation. The general results show that the influence of an impurity strongly depends on its type. Indeed, an acceptor or a donor will create a repulsive or attractive potential, giving rise to tunneling effect or resonances, respectively. Our calculations analyze the impact on electron density, transmission coefficient and drain current (I(D)) which undergoes variations up to 50%. This pinpoints the importance of intrinsic fluctuations due to doping in ultimate nano-transistors whose magnitude cannot be neglected in the next generations of integrated circuits. (C) 2008 Elsevier Ltd. All rights reserved
Physically based diagonal treatment of the self-energy of polar optical phonons. Performance assessment of III-V double-gate transistors
No full textWe propose a diagonal approximation for the self-energy that describes the interaction between electrons and polar optical phonons in the framework of nonequilibrium Green's function transport simulations. Our model is based on the definition of a scaling factor, which renormalizes the local electron-phonon coupling, to take into account the nonlocality of the interaction and provide the correct scattering rates. While previous studies relied on empirical values of this factor, we derive, from basic physical relationships, analytical expressions in the presence of the one- and two-dimensional confinement of phonons. We apply our model to the self-consistent simulation of double-gate p-type transistors made of technologically relevant III-V materials (InAs, InSb, and GaSb). Their performance is benchmarked, for different crystallographic orientations and strain constraints, against the corresponding Si and Ge devices. We find that the electron-polar optical phonon scattering plays a major role in degrading the performance of the III-V devices and typically results in a widening of the performance gap existing between III-V and Si or Ge devices in ballistic transport condition
Anharmonic phonon-phonon scattering modeling of three-dimensional atomistic transport. An efficient quantum treatment
No full textWe propose an efficient method to quantum mechanically treat anharmonic interactions in the atomistic nonequilibrium Green's function simulation of phonon transport. We demonstrate that the so-called lowest-order approximation, implemented through a rescaling technique and analytically continued by means of the Padé approximants, can be used to accurately model third-order anharmonic effects. Although the paper focuses on a specific self-energy, the method is applicable to a very wide class of physical interactions. We apply this approach to the simulation of anharmonic phonon transport in realistic Si and Ge nanowires with uniform or discontinuous cross sections. The effect of increasing the temperature above 300 K is also investigated. In all the considered cases, we are able to obtain a good agreement with the routinely adopted self-consistent Born approximation, at a remarkably lower computational cost. In the more complicated case of high temperatures (300 K), we find that the first-order Richardson extrapolation applied to the sequence of the Padé approximants N-1/N results in a significant acceleration of the convergenc
Quantum treatment of phonon scattering for modeling of three-dimensional atomistic transport
No full textBased on the nonequilibrium Green's function formalism, we show a numerically efficient method to treat inelastic scattering in multidimensional atomistic codes. Using a simple rescaling approach, we detail the calculations of the lowest-order approximation (LOA) [Y. Lee et al., Phys. Rev. B 93, 205411 (2016)2469-995010.1103/PhysRevB.93.205411] series to the usual, computationally intensive, self-consistent Born approximation (SCBA). This, combined with the analytic continuation technique of Padé approximants, is applied to an atomistic code based on a tight-binding sp3d5s∗ model for electrons and holes, and a modified valence-force-field method for phonons. Currents in Si and Ge gate-all-around nanowire transistors are then computed considering the main crystallographic transport directions ((100), (110), (111)) for both n-type and p-type devices. Our results show that in most configurations, third-order LOA currents are enough to achieve a high agreement with SCBA results, while reducing the calculation time by about one order. In addition, we propose a criterion to determine the validity of such expansion technique
Modelling the electronic structure of EL2
No full textThe levels and excitation energies of a weakly interacting AsGa - Asi defect pair have been calculated using the model energy functional introduced by Baraff and Schluter. The calculation is performed in a manner which allows the Jahn-Teller relaxation proposed by Lannoo to distort the Asi away from the symmetry site. We evaluate the parameters of the model using experimental information where possible and using the results of self consistent Greens function calculations where no experimental information is available. The isolated Asi turns out to have no equilibrium state capable of giving rise to an ESR spectrum. It has a shallow donor level plus a two-electron level (As+i , As 3+i ) in the lower half gap. This level structure persists in the defect pair, which now contains, in addition to the excitations associated with the individual defects, a charge transfer excitation in which (As 0Ga - As+i) → (As- Ga - As2+i ). The species As- Ga, which is unstable in isolation, becomes longer lived as a component of the defect pair. The calculations support the proposal of von Bardeleben et al. that the ground state of the metastable defect EL2 is, in fact, this defect pair.Les niveaux et énergies d'excitation d'une paire de défauts AsGa - Asi en faible interaction ont été calculés en utilisant une forme analytique de l'énergie introduite par Baraff et Schlüter. Le calcul est effectué de façon à tenir compte, comme l'a proposé Lannoo, de la distorsion Jahn-Teller qui déplace Asi de son site à haute symétrie. Quand c'est possible nous évaluons les paramètres du modèle à partir des résultats expérimentaux sinon nous utilisons les résultats de calculs selfconsistents par fonctions de Green. Nous trouvons que l'intersticiel Asi isolé n'a pas d'état d'équilibre susceptible de donner lieu à un spectre R.P.E.. Il présente un niveau donneur hydrogénoïde plus un niveau à deux électrons (As+i, As3+i ) dans la partie inférieure du gap. Cette structure de niveaux persiste dans la paire qui, en plus des excitations individuelles des défauts, présente une excitation avec transfert de charge (As0Ga - As+ i → (As-Ga - As2+i ). L'entité As-Ga, instable isolément, acquiert une durée de vie plus longue dans la paire. Les calculs supportent la proposition de von Bardeleben et al. qui attribue l'état fondamental de EL2 à la paire AsGa - Asi
Stability of electronic states of the vacancy in diamond
No full textThe vacancy in diamond is a fundamental defect which has been studied theoretically and experimentally for forty years. However, although early theories (Coulson C A and Kearsley M J 1957 Proc. R. Soc. A 241 433) were extremely successful in explaining the nature of the ground state of the neutral defect and the Jahn-Teller distortion expected (Lannoo M and Stoneham A M 1968 J. Phys. Chem. Solids 29 1987), there are still several questions which have not been answered satisfactorily. in particular, the many-electron effects and configuration interaction are vital. They determine not only the order of electronic levels in the vacancy, but also the best-known optical transition. GR1, which cannot be expressed in terms of one-electron levels alone.We bring together much of the derailed recent experimental data on the different charge states and excited states of the vacancy to build up a simple empirical model of the defect. We show that the stability of the states and their photoconductivity, or lack of it, can be reproduced. We can predict that other states of the neutral vacancy, observable by EPR, lie very close above the ground state. and another high-energy optical transition might be detectable
Physically based diagonal treatment of polar optical phonons in III-V p-type double-gate transistors: comparison of InAs vs Ge and Si
No full text- …
