MOLECULAR SPUTTERING AND DAMAGE INDUCED BY keV IONS IN MULTILAYERED LANGMUIR-BLODGETT FILMS

Les effets d'irradiation (érosion et endommagement) induits par des ions de faible énergie (keV) dans des films de Langmuir-Blodgett de différentes épaisseurs ont été étudiés à différents angles d'incidence pour des doses ⩽ 3 x 1013 ions.cm-2. Ces films, composés de monocouches superposées et distinctes, permettent de suivre en spectrométrie de masse d'ions secondaires (SIMS) l'évolution, au cours du bombardement, de l'intensité de l'ion moléculaire associé à une profondeur donnée. Au voisinage de l'incidence normale, le volume excité par l'ion primaire est caractérisé par une extension radiale faible par rapport à son extension en profondeur.The irradiation effects (sputtering and damage) induced by keV ion in Langmuir-Blodgett films of different thickness are studied for different incidence angles and for doses up to 3 x 1013 ions.cm-2. The films composed of different superposed monolayers allow to study, in SIMS, the evolution of the molecular ion intensity as a function of film depth. The volume excited by the primary ion is characterized at small incidence angle by a small radial extension with respect to its depth extension

ÉTUDE DE LA RÉPARTITION DES IONS ET DES DÉFAUTS CRÉÉS PAR IMPLANTATION DANS LES SEMI-CONDUCTEURS PAR INTERFÉROMÉTRIE INFRAROUGE

Des interférences apparaissent dans les spectres de réflectivité infrarouge effectués sur des couches épitaxiées sur des semi-conducteurs fortement dopés. Nous avons approfondi l'étude de ce phénomène sur des couches présentant une interface abrupte (substrats dopés à l'arsenic). Nous avons mis en évidence des interférences dans les spectres de réflectivité d'échantillons implantés (bore et phosphore ; 1-2 MeV ; recuit à 950 °C). Nous avons observé des pièges à électrons créés par implantation – avant recuit – sur des échantillons uniformément dopés (≈ 1019 e/cm3) et implantés. Nous concluons que l'interférométrie infrarouge est une bonne méthode pour l'étude des inhomogénéités superficielles des semi-conducteurs.Interferences appear in infrared reflectivity spectra observed on epitaxial layers on heavily doped semiconductors. We deepened the study of this phenomenon on layers which have a sharp interface (arsenic doped substrates). We observed interferences in the reflectivity spectra of implanted samples (boron and phosphorus ; 1-2 MeV ; annealed at 950 °C). Electron traps created by implantation have been observed – before annealing – on uniformly doped (≈ 1019 e/cm3) implanted samples. We conclude that the infrared interferometry is a good method for the study of superficial inhomogeneity of semiconductors

Protein tyrosine kinases and protein tyrosine phosphatases are involved in abscisic acid-dependent processes in Arabidopsis seeds and suspension cells.

International audienceProtein tyrosine (Tyr) phosphorylation plays a central role in many signaling pathways leading to cell growth and differentiation in animals. Tyr phosphorylated proteins have been detected in higher plants, and the roles of protein Tyr phosphatases and protein Tyr kinases in some physiological responses have been shown. We investigated the involvement of Tyr phosphorylation events in abscisic acid (ABA) signaling using a pharmacological approach. Phenylarsine oxide, a specific inhibitor of protein Tyr phosphatase activity, abolished the ABA-dependent accumulation of RAB18 (responsive to ABA 18) transcripts. Protein Tyr kinase inhibitors like genistein, tyrphostin A23, and erbstatin blocked the RAB18 expression induced by ABA in Arabidopsis (Arabidopsis thaliana). Stomatal closure induced by ABA was also inhibited by phenylarsine oxide and genistein. We studied the changes in the Tyr phosphorylation levels of proteins in Arabidopsis seeds after ABA treatment. Proteins were separated by two-dimensional gel electrophoresis, and those phosphorylated on Tyr residues were detected using an anti-phosphotyrosine antibody by western blot. Changes were detected in the Tyr phosphorylation levels of 19 proteins after ABA treatment. Genistein inhibited the ABA-dependent Tyr phosphorylation of proteins. The 19 proteins were analyzed by matrix-assisted laser-desorption ionization time-of-flight/time-of-flight mass spectrometry. Among the proteins identified were storage proteins like cruciferins, enzymes involved in the mobilization of lipid reserves like aconitase, enolase, aldolase, and a lipoprotein, and enzymes necessary for seedling development like the large subunit of Rubisco. Additionally, the identification of three putative signaling proteins, a peptidyl-prolyl isomerase, an RNA-binding protein, and a small ubiquitin-like modifier-conjugating enzyme, enlightens how Tyr phosphorylation might regulate ABA transduction pathways in plants