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Claudio Grimaldi

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Publications associées (54)

Optimal percolation of disordered segregated composites

Thomas Maeder, Peter Ryser, Claudio Grimaldi, Niklaus Johner

We evaluate the percolation threshold values for a realistic model of continuum segregated systems, where random spherical inclusions forbid the percolating objects, modellized by hard-core spherical particles surrounded by penetrable shells, to occupy lar ...

2009

Electron tunneling in conductor-insulator composites with spherical fillers

Gianluca Ambrosetti, Thomas Maeder, Peter Ryser, Claudio Grimaldi, Niklaus Johner

We report on our Monte Carlo calculations of the conductivity of monosized and conducting spherical particles dispersed in a homogeneous matrix, with interparticle transport mechanism given by electron tunneling. We show that our numerical results can be r ...

2009

Weak-and strong-coupling limits of the two-dimensional Frohlich polaron with spin-orbit Rashba interaction

Claudio Grimaldi

The continuous progress in fabricating low-dimensional systems with large spin-orbit couplings has reached a point in which nowadays materials may display spin-orbit splitting energies ranging from a few to hundreds of meV. This situation calls for a bette ...

2008

Energy levels of a two-dimensional hydrogen atom with spin-orbit Rashba interaction

Claudio Grimaldi

Electronic bound states around charged impurities in two-dimensional systems with structural inversion asymmetry can be described in terms of a two-dimensional hydrogen atom in the presence of a Rashba spin-orbit interaction. Here, the energy levels of the ...

2008

Percolative properties of hard oblate ellipsoids of revolution with a soft shell

Gianluca Ambrosetti, Peter Ryser, Claudio Grimaldi, Niklaus Johner

We present an in-depth analysis of the geometrical percolation behavior in the continuum of random assemblies of hard oblate ellipsoids of revolution. Simulations were carried out by considering a broad range of aspect-ratios, from spheres up to aspect-rat ...

2008

Transport exponent in a three-dimensional continuum tunneling-percolation model

Peter Ryser, Claudio Grimaldi, Niklaus Johner

The tunneling-percolation mechanism of conduction in disordered conductor-insulator composites is studied for a realistic continuum model where conducting and impenetrable spherical particles are dispersed in a three-dimensional continuum insulating materi ...

2008

Electron-phonon interaction and charge carrier mass enhancement in SrTiO3

Claudio Grimaldi, Dirk Van der Marel

We report a comprehensive THz, infrared and optical study of Nb-doped SrTiO3 as well as dc conductivity and Hall effect measurements. Our THz spectra at 7 K show the presence of an unusually narrow (< 2 meV) Drude peak. For all carrier concentrations the D ...

2008

Apparent nonuniversality in finite segregated tunneling-percolaiton models

Peter Ryser, Claudio Grimaldi, Niklaus Johner

We investigate the tunneling-percolation mechanism of DC transport nonuniversality for conducting particles of diameter Φ placed in series within the bonds of length Lof a regular lattice model. When L/Φ→∞ the resulting bond conductance distribution functi ...

2007

Piezoresistivity and tunneling-percolation transport in apparently nonuniversal systems

Peter Ryser, Claudio Grimaldi, Niklaus Johner

We formulate a generalized tunneling-percolation model that describes the electrical properties of conductor-insulator cellular disordered systems. This model predicts and explains the experimentally observed universal and nonuniversal behaviors of such pr ...

2007

Properties and stability of thick-film resistors with low processing temperatures - effect of composition and processing parameters

Thomas Maeder, Claudio Grimaldi, Sonia Vionnet Menot, Caroline Jacq

In this work, the properties (sheet-resistance, temperature coefficient and piezoresistance / gauge factor) and stability of thick-film resistors with low firing temperatures (525...650°C) are studied. To this end, two low-melting lead borosilicate glass c ...

2006

High-Voltage Sensitivity Studies of Model Thick-Film Resistors

Thomas Maeder, Peter Ryser, Claudio Grimaldi, Niklaus Johner, Adrian Kambli, Caroline Jacq

In this work we seek to better understand the mechanisms governing pulse voltage trimming in disordered conductor-insulator composites. Therefore, we investigate the effect of the composition of thick-film resistors (TFRs) on sensitivity to high voltage pu ...

2006

Tunneling and nonuniversality in continuum percolation systems

Claudio Grimaldi

The values obtained experimentally for the conductivity critical exponent in numerous percolation systems, in which the interparticle conduction is by tunneling, were found to be in the range of t0 and about t0 + ...

2006

Tunneling-percolation origin of nonuniversality: Theory and experiments

Thomas Maeder, Peter Ryser, Claudio Grimaldi, Sonia Vionnet Menot

A vast class of disordered conducting-insulating compounds close to the percolation threshold is characterized by nonuniversal values of transport critical exponent t, in disagreement with the standard theory of percolation which predicts t ...

2005

Study of electrical properties of piezoresistive pastes and determination of the electrical transport

Thomas Maeder, Peter Ryser, Claudio Grimaldi, Sonia Vionnet Menot

A vast class of disordered conducting-insulating compounds close to the percolation threshold is characterized by nonuniversal values of transport critical exponents. The lack of universality implies that critical indexes may depend on material properties ...

2005

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