Papers by Jean-marc Costantini
Journal of Non-crystalline Solids, Aug 1, 1997
We have studied the luminescence of natural SiO2 quartz induced by irradations with heavy ions in... more We have studied the luminescence of natural SiO2 quartz induced by irradations with heavy ions in the MeV amu−1 range. The spectra obtained with sample temperatures of ∼ 85 K have the same features and line shapes, irrespective of the fluence (φt) and electronic stopping power (Se) of the different ions (from 12C to 127I). The spectra are least-squares fitted
Journal of Applied Physics, Oct 15, 2009
This work aims specifically at studying the evolution of point defects induced by electron irradi... more This work aims specifically at studying the evolution of point defects induced by electron irradiation in the cubic polytype of SiC (3C-SiC) at temperatures ranging from 10 to 1450 K by means of photoluminescence (PL) spectroscopy. We identified a first annealing stage between 200 and 245 K, which probably results from migration of interstitials in the carbon sublattice. Moreover, we confirmed the high thermal stability of defect-related PL signals up to about 1100 K and calculated the activation energies associated with their annihilation. Finally, we studied the effect of a high temperature treatment at 1400 K on the DI center PL intensity in a single-crystal sample irradiated by electrons below the threshold displacement energy of the silicon sublattice. This allows checking the relevance of recent defect models based upon the migration of atoms in the carbon sublattice during the irradiation process. We conclude that the DI center does not involve the silicon vacancy and could be assigned to an isolated silicon antisite SiC.
Journal of Nuclear Materials, Feb 1, 2003
We have studied the depth profiles of 3He implanted into tantalum with concentrations ranging bet... more We have studied the depth profiles of 3He implanted into tantalum with concentrations ranging between 500 and 2500 at.ppm. We used the 3He nuclear reaction analysis based on the 3He(d,p)4He ‘resonant’ reaction which yields a specific signal, independent of the Ta host. Excitation curves were obtained by measuring the 13-MeV proton yield as a function of the incident deuteron energy
The objective of the present work is to study the irradiation effects on third generation SiC fib... more The objective of the present work is to study the irradiation effects on third generation SiC fibers which fulfill the minimum requisites for nuclear applications, i.e. Hi-Nicalon type S, hereafter HNS, and Tyranno SA3, hereafter TSA3. With this purpose, these fibers have been ionirradiated with 4 MeV Au ions at RT and increasing fluences. Irradiation effects have been characterized in terms of micro-Raman Spectroscopy (µRS) and Transmission (TEM) and compared to the response of the as-irradiated model material, i.e. 6H-SiC single crystals. It is reported that ion-irradiation induces amorphization in SiC fibers. Ion-amorphization kinetics between these fibers and 6H-SiC single crystals are similar despite their different microstructures and polytypes with a critical amorphization dose of ~3×10 14 cm-2 (~0.6 dpa) at RT. Also, thermally annealing induced cracking is studied via in-situ Environmental Scanning Electron Microscopy (E-SEM). The temperatures at which the first cracks appear as well as the crack density growth rate increase with increasing heating rates. The activation energy of the cracking process yields 1.05 eV in agreement with recrystallization activation energies of ion-amorphized samples.
Journal of Physics D, Apr 14, 1993
The amorphization process of yttrium iron garnet (YIG) epitaxial films, caused by irradiation wit... more The amorphization process of yttrium iron garnet (YIG) epitaxial films, caused by irradiation with 235 MeV 84Kr ions, has been studied by high-resolution diffraction techniques. For this purpose, the X-ray rocking curves of the (888) reflection, at a Bragg angle of around 60 degrees , were recorded at increasing ion fluences using a five-crystal diffractometer. It is shown that in-plane
Journal of Applied Physics, May 1, 2000
The room-temperature dc conductivity is used to monitor the damage and structural modifications i... more The room-temperature dc conductivity is used to monitor the damage and structural modifications induced by swift heavy ion irradiations in yttrium iron garnet (Y3Fe5O12 or YIG) epitaxial layers doped with calcium (CaYIG) or silicon (SiYIG), with a variable conductivity due to a variable degree of compensation, and amorphous YIG layers. Irradiations are performed with heavy ions in the 0.8–6 MeV amu−1 energy range, in the electronic slowing down regime, with an electronic stopping power ranging between 7 and 41 MeV μm−1 above the amorphous track formation threshold (4.5 MeV μm−1) in this low-ion velocity range. A conductivity decrease versus ion fluence is found in the case of the high-conductivity uncompensated epilayers whereas an increase occurs for the low-conductivity compensated ones, either p-type (CaYIG) or n-type (SiYIG). These results are discussed by considering the competing effects of disorder on the carrier density and mobility in the case of compensated and uncompensated semiconductors. In both cases, the low-fluence data display a plateau at around the same conductivity value corresponding to the amorphous YIG above an amorphous fraction around 50% regardless of the ions. All the high-fluence data exhibit a power-law behavior without saturation, above a threshold fluence decreasing with increasing amorphization cross section (A). These results are interpreted by the formation of amorphous tracks and of a more conducting nanophase after recrystallization of the tracks under ion impacts. All the data are rescaled versus the product of A times fluence (φ) where amorphization dominates for Aφ⩽1, whereas recrystallization dominates for Aφ>10. However, significantly larger A values than the ones previously determined from the RBS-channeling data are derived from a mean-field analysis of the low-fluence conductivity data with a 2D Bruggeman model. These deviations are ascribed to a contribution of the crystalline track halos where internal stresses are accumulated due to the atomic density difference between the crystal and amorphous phase. A simple phenomenological approach of the amorphization and recrystallization processes is proposed on the basis of two kinetic rate equations with a recrystallization cross section (S) at least one order of magnitude smaller than A. These S values are in agreement with a thermal spike model assuming vaporization of the amorphous YIG phase along the ion path. At such high temperatures in the ion tracks, the garnet phase may decompose into a more conducting nanocrystalline phase. Finally, an exp(−T)−1/4 law for the thermal dependence of conductivity at low temperature is found in the nanophase like in the amorphous one, most probably because of the strong contribution of the disordered grain boundary cores in the conduction process.
Journal of Nuclear Materials, Oct 1, 2011
Oxide Dispersion Strengthened (ODS) ferritic/martensitic (F/M) steels are promising materials as ... more Oxide Dispersion Strengthened (ODS) ferritic/martensitic (F/M) steels are promising materials as structural components for fusion reactors. Their excellent creep properties are provided by the nano-dispersed oxides reinforcing the material. This oxide dispersion has to be as stable as possible under irradiation at high temperatures.In the present work, low and high energy ion irradiation experiments were used to investigate microstructural stability under irradiation of oxides. Two iron base ODS alloys were studied: the ODS DY reinforced by yttrium and titanium oxides and the ODS EM10 reinforced by magnesium oxides. TEM investigations of the crystallinity for large oxides (d≈50nm) after irradiations reveal that, in both alloys, amorphization can occur due to electronic excitations or ballistic damages. Amorphization appears to depend on the nature of the oxides. Low energy ion irradiation results show that a critical temperature and a critical dose may exist, for which no amorphization is observed.
Philosophical Magazine, Oct 21, 2014
Silicon carbide (SiC) single crystals with the 6H polytype structure were irradiated with 4.0-MeV... more Silicon carbide (SiC) single crystals with the 6H polytype structure were irradiated with 4.0-MeV Au ions at room temperature (RT) for increasing fluences ranging from 1 × 10 12 to 2 × 10 15 cm −2 , corresponding to irradiation doses from~0.03 to 5.3 displacements per atom (dpa). The damage build-up was studied by micro-Raman spectroscopy that shows a progressive amorphization by the decrease and broadening of 6H-SiC lattice phonon peaks and the related growth of bands assigned to Si-Si and CC homonuclear bonds. A saturation of the lattice damage fraction deduced from Raman spectra is found for~0.8 dpa (i.e. ion fluence of 3 × 10 14 cm −2). This process is accompanied by an increase and saturation of the out-of-plane expansion (also for~0.8 dpa), deduced from the step height at the sample surface, as measured by phase-shift interferometry. Isochronal thermal annealing experiments were then performed on partially amorphous (from 30 to 90%) and fully amorphous samples for temperatures from 200°C up to 1500°C under vacuum. Damage recovery and densification take place at the same annealing stage with an onset temperature of~200°C. Almost complete 6H polytype regrowth is found for partially amorphous samples (for doses lower than 0.8 dpa) at 1000°C, whereas a residual damage and swelling remain for larger doses. In the latter case, these unrelaxed internal stresses give rise to an exfoliation process for higher annealing temperatures.
Journal of Nuclear Materials, Oct 1, 2011
Owing to their low swelling under irradiation and excellent creep properties, oxide dispersion st... more Owing to their low swelling under irradiation and excellent creep properties, oxide dispersion strengthened (ODS) materials are expected to play an important role as structural components for fusion reactors. These materials are reinforced by a nano-oxide dispersion. Hence, to ensure their good in-reactor mechanical properties, ODS materials have to keep their nano-size precipitates stable under neutron irradiation. The structural stability under irradiation of the oxides is analyzed in a Fe-18Cr-1W-0.3Ti alloy reinforced by 0.5Y 2 O 3 upon high-energy ion irradiations (92-MeV Xe) at room temperature (300 K) and at 780 K up to a fluence of 3 Â 10 14 cm À2. The use of high-energy heavy ions allows a specific study of the effect of electronic interactions and low ballistic damages on oxides. Results provided by transmission electron microscopy show that the precipitates could exhibit an amorphization after irradiation at room temperature whereas the particles remain crystalline after irritation at 780 K.
Journal of Nuclear Materials, Sep 1, 2023
Journal of Solid State Chemistry, Apr 1, 1983
A study was made of the influence of the chalcogen X on the magnetic and electrical properties of... more A study was made of the influence of the chalcogen X on the magnetic and electrical properties of Pu2O2X (X = O, S, Se) compounds and on bonding in these hexagonal compounds, isostructural with the corresponding rare-earth compounds. The comparison of the cell volumes of Nd2O2X and Pu2O2X compounds showed that the Pu3+ crystal radius decreased from beta-Pu2O3 to Pu2O2Se as ``5f delocalization'' and 5f-p overlap increased. These plutonium compounds were all found to be antiferromagnetic. This was caused by superexchange coupling interactions via p orbitals of the oxygen and chalcogen ions. The Néel temperature increased from beta-Pu2O3 (26 K) to Pu2O2S (28 K) then to Pu2O2Se (34 K) showing that 5f-p covalency was enhanced as the chalcogen electronegativity decreased and the p radial extent increased. The hexagonal beta-Pu2O3 was found to be an insulator while both other compounds were semiconductors with gaps around 0.5 eV. These gaps were interpreted as the energy separation between the 6d-7s conduction band and the np band of the chalcogen X with some overlap of the occupied 5f states and the np band. A simple electron band scheme of these compounds is proposed on such assumptions. Nous avons étudié l'influence de l'élément chalcogène X sur les propriétés magnétiques et électriques des oxychalcogénures Pu2O2X (X = O, S, Se) ainsi que sur la liaison chimique dans ces composés hexagonaux, isostructuraux des composés similaires de terres rares. En comparant les volumes de maille de Pu2O2X et de Nd2O2X, on montre que le rayon cristallin de Pu décroit de Pu2O3à Pu2O2Se avec l'augmentation des recouvrements 5f-p et de la ``délocalisation'' des électrons 5f. Ces composés sont tous antiferromagnétiques, la température de Néel augmentant de Pu2O3 (26 K) à Pu2O2Se (34 K). Cela montre que, lorsque l'électronégativité de X diminue, les interactions de superéchange à travers O2- et X2- se renforcent ainsi que la covalence 5f-p. Pu2O3 hexagonal est isolant alors que les deux autres composés sont semiconducteurs avec un gap voisin de 0,5 eV. Nous avons considéré ce gap comme la différence d'énergie entre la bande de conduction 7s-6d et la bande np du chalcogène X. Les états 5f occupés sont situés juste au-dessous de la bande np en la recouvrant partiellement. A partir de ces hypothèses nous avons proposé un modèle de bandes simple pour ces composés.
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, Apr 1, 1990
An analytical procedure and a simulation-optimization algorithm are described for hydrogen determ... more An analytical procedure and a simulation-optimization algorithm are described for hydrogen determination based on elastic recoil detection induced by low-energy 4He ions (I 3 MeV) using transmission geometry. Hydrogen concentration depth profiles can be derived from the experimental recoil spectra for a depth range of up to 6 pm with a resolution better than 40 nm at the surface. The method is applied to thin polyimide films irradiated by high-energy heavy ions. The 3D hydrogen distribution is determined with a 4He+ microbeam. A high-hydrogen-concentration xone below the surface is shown. The hydrogen distribution is seen ,to evolve during the 4He+ irradiation.
Physical Review B, Feb 15, 2012
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
Journal of Applied Physics, May 19, 2023
Epitaxial cubic (100) 3C-SiC films on a (100) silicon wafer were irradiated at room temperature w... more Epitaxial cubic (100) 3C-SiC films on a (100) silicon wafer were irradiated at room temperature with 2.3-MeV Si+ or 3.0-MeV Kr+ ions up to a fluence of 1 × 1016 cm−2. The evolutions of the epilayer and the substrate were followed as a function of ion fluence by using micro-Raman spectroscopy, optical absorption, and diffuse reflectance spectroscopy in the UV-visible and near infrared range. Raman spectra evidence the amorphization of SiC films at an estimated dose of about 0.1 displacement per atom (dpa) for both ion irradiations. The narrow peaks of the Raman-allowed TO and LO modes of SiC and Si are recorded in the virgin sample, together with few peaks assigned to zone-edge modes of SiC arising from the intrinsic disorder in the strained films. Those crystal phonon peaks broaden or disappear with increasing fluence. The spectra finally exhibit broad extra peaks assigned to the formation of Si–Si and C–C wrong homonuclear bonds in the local order of the amorphous phase. The optical transmission and diffuse reflectance spectra feature interference fringe patterns in the SiC film that are smoothened out with irradiation due to the matching of refractive indices of the amorphous SiC film and Si substrate. The evolution of the refractive index of SiC and optical gap of Si are deduced from those spectra. The respective roles of ballistic effects and electronic excitations in the radiation damage of both SiC and Si are discussed for those two ions with about the same electronic stopping power and about one order-of-magnitude difference in nuclear stopping power. The damage is dominated by the nuclear collision processes and rather well correlated with the estimated irradiation dose in dpa. Optical spectra show that electronic excitations induce damage recovery of the amorphized substrate below the SiC/Si interface. Raman spectra and optical absorption/reflection spectra yield complementary pictures of the radiation damage.
Journal of Physics and Chemistry of Solids, Oct 1, 2022
Philosophical Magazine, Nov 13, 2014
Yttria-stabilized zirconia (YSZ) single crystals (for 9.5 and 18 mol% yttria) were irradiated at ... more Yttria-stabilized zirconia (YSZ) single crystals (for 9.5 and 18 mol% yttria) were irradiated at room temperature (RT) by X-rays (W white spectrum) and 2.5-MeV electrons. The growth curves of the so-called T-centre (for trigonal centre, i.e. Zr3+ sitting in a trigonal symmetry site) were studied as a function of absorbed dose, or irradiation time, by UV–visible optical absorption (OA) spectroscopy and X-band electron paramagnetic resonance spectroscopy. The defect concentration at saturation and the production rate are increased by a factor around two for 18 mol% yttria with respect to 9.5 mol%. Defect decay was then followed after irradiation by OA spectroscopy as a function of ageing time at RT. Growth and decay curves of the T-centre are modelled on the basis of rate equations of charge-exchange reactions with the zirconium lattice ions. Increase in yttrium content is thought to decrease hole trapping on Zr3+ ions, thereby enhancing T-centre formation.
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, Mar 1, 1991
... tomatic simulation optimization algorithm (GABY code) developed by Tirira et al. [13]. A deut... more ... tomatic simulation optimization algorithm (GABY code) developed by Tirira et al. [13]. A deuteron microbeam (1.45 MeV) is used to de-termine C, N and 0 contents in irradiated kapton 0168-583X/91/$03.50 1991 - Eisevier Science Publishers BV (North-Holland) P. Trocellier et ...
Journal of Solid State Chemistry, Apr 1, 1983
We describe the preparation and some physical properties of Pu2O2Te. The plutonium oxide tellurid... more We describe the preparation and some physical properties of Pu2O2Te. The plutonium oxide telluride is isostructural with the corresponding rare-earth oxide tellurides which crystallize in the tetragonal system of La2O2Te-type. Magnetic susceptibility data from 4 K to room temperature are reported together with resistivity measurements. Pu2O2Te is found to be an antiferromagnet below 56 K and a semiconductor with an intrinsic energy gap of 0.65 eV. The magnetic behavior is interpreted in terms of superexchange coupling interactions via nonmetal p orbitals, i.e., in terms of 5f-p overlaps. This conclusion is supported by crystal chemistry considerations by comparison of cell volumes of Pu2O2Te and Nd2O2Te. In Pu2O2Te, the Pu crystal radius is found to be much lower than that of Nd in Nd2O2Te, suggesting some 5f electron ``delocalization'' leading to a crystal radius shrinkage. As for the hexagonal Pu2O2X compounds, with X = O, S, Se, the measured gap may be considered as the energy separation between the chalcogen np band and the 6d-7s conduction band, the occupied 5f states lying just below the np band with some 5f-np overlap. Nous décrivons la préparation et quelques propriétés physiques de Pu2O2Te. L'oxytellurure de plutonium est isostructural des oxytellurures correspondants de terres rares qui cristallisent dans le système quadratique de type La2O2Te. On a mesuré sa susceptibilité magnétique ainsi que sa résistivité entre 4 K et la température ambiante. Pu2O2Te est antiferromagnétique au-dessous de 56 K et semiconducteur avec un gap intrinsèque de 0.65 eV. Le magnétisme a été interprété en terme d'interactions de superéchange à travers les orbitales p des non-métaux c'est-à-dire en terme de recouvrements 5f-p. Cette conclusion est confirmée par des considérations cristallochimiques en comparant les volumes de maile de Pu2O2Te et de Nd2O2Te. Dans Pu2O2Te, le rayon cristallin de Pu est bien inférieur à celui de Nd dans Nd2O2Te. Cela suggère que les électrons 5f se ``délocalisent'' ce qui conduit à une réduction du rayon cristallin. Comme pour les composés hexagonaux Pu2O2X oùX = O, S, Se le gap mesuré peut être considéré comme la différence d'énergie entre la bande np du chalcogène, et la bande de conduction 6d-7s, les états 5f occupés se trouvant juste au-dessous de la bande np en la recouvrant partiellement.
Radiation Effects and Defects in Solids, Nov 1, 1990
... Instr. andkfeth. B34,337 (1988). 13. L. Forro, J. Mory and L. Zuppiroli, to be published (199... more ... Instr. andkfeth. B34,337 (1988). 13. L. Forro, J. Mory and L. Zuppiroli, to be published (1990). 14. A. Dunlop, D. Lesueur and J. D ud , NucL Insfr. andMefh. B42, 182 (1989). 15. RS Averbach, R. Benedek and K. L. Merkel, Phys. Rev. B18,4156 (1978). State 31,6 (1989).
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 1993
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Papers by Jean-marc Costantini