Marcel Toulemonde

Bio: Marcel Toulemonde is an academic researcher from Centre national de la recherche scientifique. The author has contributed to research in topics: Ion & Irradiation. The author has an hindex of 53, co-authored 345 publications receiving 11518 citations. Previous affiliations of Marcel Toulemonde include University of Caen Lower Normandy & École nationale supérieure d'ingénieurs de Caen.

Transient thermal process after a high-energy heavy-ion irradiation of amorphous metals and semiconductors

Abstract: Following a description used to explain a phase transformation observed after pulsed femtosecond laser irradiation, a transient thermal process is used to describe latent-track formation after high electronic excitation induced by energetic (GeV) heavy ions. The transient thermal calculation is restricted to the amorphous materials a-Ge, a-Si, and a-${\mathrm{Fe}}_{85}$${\mathrm{B}}_{15}$, for which nearly all latent-track radii and/or macroscopic thermodynamic properties are known. The heat-flow equation is solved numerically in cylindrical geometry. The time-dependent heat-generation term is assumed to be due to the electron-atom interaction. The characteristic length \ensuremath{\lambda} of the energy transport by secondary electrons is taken as the only free parameter and the maximum diameter of the cylinder of liquid matter is considered as the diameter of the observed latent track. Using the single value \ensuremath{\lambda}=14 nm, we have been able to calculate these diameters in a-Si and a-Ge in reasonable agreement with experimental track diameters, taking into account the large differences between the macroscopic thermodynamic parameters of both materials. This \ensuremath{\lambda} value is less than that for the crystalline state. In the case of a-${\mathrm{Fe}}_{85}$${\mathrm{B}}_{15}$, the diameters calculated with use of \ensuremath{\lambda}=19 nm are in agreement with the ones determined recently by electrical-resistivity change.

The Se sensitivity of metals under swift-heavy-ion irradiation: a transient thermal process

Abstract: In the framework of the thermal-spike model the present paper deals with the effect of the electronic stopping power (Se) in metals irradiated by swift heavy ions. Using the strength of the electron-phonon coupling g(z) with the number of valence electrons z as the unique free parameter, the increment of lattice temperature induced by swift-heavy-ion irradiation is calculated. Choosing z=2, the calculated threshold of defect creation by Se for Ti, Zr, Co and Fe is about 11, 27.5, 28 and 41 keV nm-1, in good agreement with experiment. Taking the same z value, the calculation shows that Al, Cu, Nb and Ag are Se insensitive. Moreover, in Fe, the differences in the damage created by U ions of different energies but exhibiting the same value of Se may be interpreted by a velocity effect. Using z=2, other calculations suggest that Be (Se>or=11 keV nm-1), Ga (Se>or=5 keV nm-1) and Ni (Se>or=49 keV nm-1) should be sensitive to Se but Mg should not. These examples put the stress on the effect of the physical parameters governing the electron-phonon coupling constant apart from z determination: the sound velocity linked to the Debye temperature and the lattice thermal conductivity. Furthermore, a simple criterion is proposed in order to predict the Se sensitivity of metals.

Transient thermal processes in heavy ion irradiation of crystalline inorganic insulators

Abstract: A review of matter transformation induced in crystalline inorganic insulators by swift heavy ions is presented. The emphasis is made on new results obtained for amorphizable materials such as Gd3Ga5O12, GeS, and LiNbO3 and for non-amorphizable crystals such as SnO2, LiF and CaF2. Assuming that latent tracks result from a transient thermal process, a quantitative development of a thermal spike is proposed. The only free parameter is the electron–lattice interaction mean free path λ. With this parameter it is possible to quantitatively describe track radii, whatever the bonding character of the crystal is, in a wide range of ion velocities assuming two specific criteria: tracks may result from a rapid quenching of a cylinder of matter in which the energy deposited on the lattice has overcome either the energy necessary to reach a quasi-molten phase in the case of amorphizable materials or the cohesion energy in the case of non-amorphizable materials. The evolution of the λ parameter versus the band gap energy of the considered insulator will be presented. On the basis of this discussion some predictions are developed.

Track formation in SiO2 quartz and the thermal-spike mechanism.

Abstract: [alpha]-quartz has been irradiated with heavy ions: [sup 19]F, [sup 32]S, and [sup 63]Cu at an energy of about 1 MeV/amu in order to cover a range of electronic stopping powers [ital dE]/[ital dx] between 2.4 and 9 keV/nm and [sup 58]Ni, [sup 86]Kr, [sup 128]Te, [sup 129]Xe, [sup 181]Ta, and [sup 208]Pb between 1 and 5.8 MeV/amu for [ital dE]/[ital dx][gt]7 keV/nm. The extent of the induced damage is determined using Rutherford backscattering ion channeling with a 2-MeV [sup 4]He beam. The damage cross section [ital A] is obtained using a Poisson law [ital F][sub [ital d]]=1[minus]exp([minus][ital A][phi][ital t]), where [phi] is the flux and [ital t] the irradiation time. This damage cross section is linked to the effective radius [ital R][sub [ital e]] through the relation [ital A]=[pi][ital R][sub [ital e]][sup 2], where [ital R][sub [ital e]] is the radius of an equivalent cylinder of damage. Using high-resolution electron microscopy, cylinders of amorphous matter have been observed, whose radius corresponds to [ital R][sub [ital e]] when the track is continuous (i.e., for [ital A][ge]1.3[times]10[sup [minus]13] cm[sup 2]; [ital R][sub [ital e]][ge]2 nm). A thermal-spike model is applied to calculate the radii of the observed tracks assuming that themore » observed amorphous cylinders correspond to a rapid quench of a molten liquid phase along the ion path. The model is applied only when the latent track is continuous and cylindrical. A good agreement is obtained taking into account that the initial spatial energy deposition on the electrons depends on the ion velocity.« less

Swift heavy ions in magnetic insulators: A damage-cross-section velocity effect.

Abstract: The damage in ferrimagnetic yttrium iron garnet, ${\mathrm{Y}}_{3}$${\mathrm{Fe}}_{5}$${\mathrm{O}}_{12}$ or YIG, induced by energetic heavy-ion bombardment in the electronic stopping-power regime has been studied in the low-velocity range (for a beam energy E\ensuremath{\le}3.6 MeV/amu). Epitaxial thin films of YIG on [111]-${\mathrm{Gd}}_{3}$${\mathrm{Ga}}_{5}$${\mathrm{O}}_{12}$ substrates were thus irradiated at room temperature with 15-MeV $^{19}\mathrm{F}$, 50-MeV $^{32}\mathrm{S}$, 650-MeV $^{181}\mathrm{Ta}$, 750-MeV $^{208}\mathrm{Pb}$, and 666-MeV $^{238}\mathrm{U}$. The damage-cross-section A is extracted from channeling-Rutherford-backscattering spectroscopy and compared to previous works. All the experimental results show that at one given value of dE/dx, the damage cross section is higher for low-velocity ions than for high-velocity ions over a large range of dE/dx. At constant dE/dx, the larger the difference between the ion velocities is, the larger the difference between the damage cross sections. Such a deviation might be explained by the effect of the energy deposition being more localized for the low-velocity ions than for the high-velocity ions. This work clearly indicates that the electronic stopping power is not the only key parameter in the creation of ion tracks, and that the damage cross section depends on the lateral distribution of the energy deposition.

Phd by thesis

Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Spintronics: Fundamentals and applications

Abstract: Spintronics, or spin electronics, involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. This article reviews the current status of this subject, including both recent advances and well-established results. The primary focus is on the basic physical principles underlying the generation of carrier spin polarization, spin dynamics, and spin-polarized transport in semiconductors and metals. Spin transport differs from charge transport in that spin is a nonconserved quantity in solids due to spin-orbit and hyperfine coupling. The authors discuss in detail spin decoherence mechanisms in metals and semiconductors. Various theories of spin injection and spin-polarized transport are applied to hybrid structures relevant to spin-based devices and fundamental studies of materials properties. Experimental work is reviewed with the emphasis on projected applications, in which external electric and magnetic fields and illumination by light will be used to control spin and charge dynamics to create new functionalities not feasible or ineffective with conventional electronics.

Angle-resolved photoemission studies of the cuprate superconductors

Abstract: The last decade witnessed significant progress in angle-resolved photoemission spectroscopy (ARPES) and its applications. Today, ARPES experiments with 2-meV energy resolution and $0.2\ifmmode^\circ\else\textdegree\fi{}$ angular resolution are a reality even for photoemission on solids. These technological advances and the improved sample quality have enabled ARPES to emerge as a leading tool in the investigation of the high-${T}_{c}$ superconductors. This paper reviews the most recent ARPES results on the cuprate superconductors and their insulating parent and sister compounds, with the purpose of providing an updated summary of the extensive literature. The low-energy excitations are discussed with emphasis on some of the most relevant issues, such as the Fermi surface and remnant Fermi surface, the superconducting gap, the pseudogap and $d$-wave-like dispersion, evidence of electronic inhomogeneity and nanoscale phase separation, the emergence of coherent quasiparticles through the superconducting transition, and many-body effects in the one-particle spectral function due to the interaction of the charge with magnetic and/or lattice degrees of freedom. Given the dynamic nature of the field, we chose to focus mainly on reviewing the experimental data, as on the experimental side a general consensus has been reached, whereas interpretations and related theoretical models can vary significantly. The first part of the paper introduces photoemission spectroscopy in the context of strongly interacting systems, along with an update on the state-of-the-art instrumentation. The second part provides an overview of the scientific issues relevant to the investigation of the low-energy electronic structure by ARPES. The rest of the paper is devoted to the experimental results from the cuprates, and the discussion is organized along conceptual lines: normal-state electronic structure, interlayer interaction, superconducting gap, coherent superconducting peak, pseudogap, electron self-energy, and collective modes. Within each topic, ARPES data from the various copper oxides are presented.

Small molecular weight organic thin-film photodetectors and solar cells

Abstract: In this review, we discuss the physics underlying the operation of single and multiple heterojunction, vacuum-deposited organic solar cells based on small molecular weight thin films. For single heterojunction cells, we find that the need for direct contact between the deposited electrode and the active organics leads to quenching of excitons. An improved device architecture, the double heterojunction, is shown to confine excitons within the active layers, allowing substantially higher internal efficiencies to be achieved. A full optical and electrical analysis of the double heterostructure architecture leads to optimal cell design as a function of the optical properties and exciton diffusion lengths of the photoactive materials. Combining the double heterostructure with novel light trapping schemes, devices with external efficiencies approaching their internal efficiency are obtained. When applied to an organic photovoltaic cell with a power conversion efficiency of 1.0%±0.1% under 1 sun AM1.5 illuminati...

First-principles calculations for defects and impurities: Applications to III-nitrides

Abstract: First-principles calculations have evolved from mere aids in explaining and supporting experiments to powerful tools for predicting new materials and their properties. In the first part of this review we describe the state-of-the-art computational methodology for calculating the structure and energetics of point defects and impurities in semiconductors. We will pay particular attention to computational aspects which are unique to defects or impurities, such as how to deal with charge states and how to describe and interpret transition levels. In the second part of the review we will illustrate these capabilities with examples for defects and impurities in nitride semiconductors. Point defects have traditionally been considered to play a major role in wide-band-gap semiconductors, and first-principles calculations have been particularly helpful in elucidating the issues. Specifically, calculations have shown that the unintentional n-type conductivity that has often been observed in as-grown GaN cannot be a...