Effet getter dans le silicium poly- et bicristallin : interaction de l'or et de l'oxygene avec les impuretes metalliques

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Role of oxygen in surface segregation of metal impurities in silicon poly-and bicrystals

Metal impurities at surfaces of polycrystalline silicon ribbons have been characterized by surface sensitive methods. Oxygen and heat treatments were found to be a driving force for surface segregation of these impurities. To better analyse their influence and their possible incidence in gettering, model studies were undertaken on Czochralski grown silicon bicrystals. Two main factors of surface segregation have been studied : the role of a ultra-thin oxide layer and the effect of heat treatments. The best surface purification was obtained after an annealing process at 750 °C of a previously oxidized surface at 450 °C. This was related to the formation of SiO clusters, followed by a coalescence of SiO4 units leading to the subsequent injection of silicon self-interstitials in the lattice.Nous avons caractérisé, au moyen des méthodes d'analyse des surfaces, les impuretés métalliques situées sur des rubans de silicium polycristallin. L'oxygène et les traitements thermiques semblent une force motrice pour la ségrégation superficielle de ces impuretés. Pour mieux étudier leur influence et leurs possibilités en terme d'effet getter, nous avons initié des études de modélisation sur des bicristaux de type Czochralski. Nous avons étudié deux facteurs principaux de ségrégation superficielle : le rôle d'une couche d'oxyde très mince et celui de traitements thermiques. Nous avons remarqué que le maximum de purification des surfaces était obtenu après le recuit à 750 °C d'une surface préalablement oxydée à 450 °C. Nous avons relié cela à la formation d'amas de SiO, suivie d'une coalescence donnant des unités de type SiO4 entraînant l'injection d'auto-interstitiels de silicium dans le réseau

Mesoporous nanomaterials based on manganese with different interlayer alkali cations: An efficient approach for the removal of Pb(II) and Cd(II) from aqueous medium

International audienceThe unique properties of nanomaterials provide a promising solution for environmental applications. Thus, three nanomaterials based on manganese birnessite-type in the form of well-structured nanowires and nanoflowers were synthesized by soft hydrothermal treatment, simple economical and without adding reagents or any other processes. Interlayer alkali cations (K+, H+ and Na+) inserted in the birnessite structure have demonstrated their effect on the structural and morphological properties of the nanomaterials and consequently on their metal ions removal efficiency. K-MnO2 nanowires with inserted K+ ions were characterized by high performance in short processing time (5 min) compared to other nanomaterials. The maximum adsorption quantities were respectively for Pb(II): K-MnO2 (300 mg/g)<Na-MnO2 (297.62 mg/g)<H-MnO2 (286.75 mg/g), and for Cd(II): K-MnO2 (228 mg/g)<Na-MnO2 (199 mg/g)<H-MnO2 (189.84 mg/g). The performance was high and stable while the nanomaterials got regenerated without losing the adsorption capacity. X-ray photoelectron spectroscopy revealed that the heavy metal ions got adsorbed onto the nanomaterials as PbO and Cd(OH)2. These results confirm the performance of non-agglomerated nanowires and nanoflowers nanomaterials based on manganese in an efficient kinetically fast metal ions removal with important stability and adsorption capacity