Processus d'agrégation dans un technosol (contribution des constituants anthropiques (oxydes de fer, laitiers, HAP, ETM) à la formation des associations organo-minérales)

Le nombre croissant de sites affectés par la présence de matériaux technogéniques rend nécessaire l étude du (bio)fonctionnement des Technosols, qui s y développent. Un matériau technogénique, issu d une ancienne friche industrielle de cokerie et présentant une multipollution en HAP et en métaux a été disposé dans des parcelles lysimétriques pour une étude in situ (site d Homécourt, www.gisfi.fr). La caractérisation morphologique et analytique à différentes échelles du matériau initial nous a permis d y définir, en analogie avec la classification pédologique standard, la présence (1) de constituants primaires tels que quartz, oxydes de fer, gypse et matières organiques anthropiques, (2) de pseudo-sables technogéniques, soit des laitiers, (3) d agrégats technogéniques stables à l eau (12% de la masse du sol) néoformés grâce au rôle agrégeant de la fraction fine (0-20 m). Matières organiques anthropiques et ETM (Zn Pb, Ba) contribuent à la formation de ces associations organo-minérales. Ce matériau d origine anthropique, tout spécifique qu il soit, contient des constituants minéraux et organiques capables de s associer et donc susceptibles, au même titre que ceux des sols naturels, d évoluer sous l effet des facteurs pédogénétiques et former ainsi un technosol. Si les deux années d expérimentation n ont pas été suffisantes pour mettre en évidence une modification de la stabilité structurale de ce jeune Technosol, les résultats y soulignent l impact des plantes colonisatrices et de la microflore rhizosphérique sur la formation d associations organo-minérales. L activité biologique est donc un facteur clef d évolution de ces solsThe increasing number of sites affected by the presence of technogenic materials makes necessary the study of (bio)functioning of Technosols, developed there. A technogenic material, resulting from an old industrial coking plant and presenting a multipollution of HAP and metals was laid out in lysimetric pieces for an in situ study (site of Homécourt, www.gisfi.fr). The morphological and analytical characterization at different scales of initial material enabled us to define, in analogy with standard pedological classification, the presence (1) of primary constituents such as quartz, iron oxides, gypsum and anthropic organic matters, (2) of technogenic pseudo-sands, like slags, (3) of water-stable technogenic aggregates (12% of the soil mass), generated through the aggregating role of the fine fraction (0-20 m). Anthropic organic matter and ETM (Zn Pb, Ba) contribute to the formation of these organo-mineral associations. This material of anthropic origin, while it is specific, contains mineral and organic components able to aggregate and is thus, as well as natural soils, able to develop under the influence of pedogenic factors to form a Technosol. If the two years of experimentation were not sufficient to highlight a modification of the structural stability of this young Technosol, the results underline there the impact of the colonizing plants and the rhizospheric microflora on the formation of organo-mineral associations. The biological activity is thus a key factor of evolution of these soilsNANCY-INPL-Bib. électronique (545479901) / SudocSudocFranceF

Comparison of oxide leakage currents induced by ion implantation and high field electric stress

International audienceWe compare in this work the electrical properties of gate leakage currents induced through the thin SiO2 oxide layer of metal-oxide-semiconductor structures by high-energy ion implantation (Boron B2+) and high field electrical stresses where electrons are injected from the gate in the Fowler–Nordheim regime. Even if the high-frequency capacitance–voltage characteristics are very different after both treatments, comparable increases and similar shapes are found at low field in static gate current–voltage curves, typical of equivalent oxide damage. Moreover, these stress or implantation induced leakage currents are both removed in a similar way by a thermal anneal under forming gas at 430°C. We conclude that similar defects could be induced through the oxide by both processes and generate those excess currents by a defect assisted tunneling mechanism

Impact of wafer charging on hot carrier reliability and optimization of latent damage detection methodology in advanced CMOS technologies

International audienceWe have studied the possibility to use hot carrier stresses to reveal the latent damage due to Wafer Charging during plasma process steps in 0.18 μm and 0.6 μm CMOS technologies. We have investigated various hot carrier conditions in N- and PMOSFETs and compared the results to classical parametric studies and short electron injections under high electric field in Fowler–Nordheim regime, using a sensitivity factor defined as the relative shift towards a reference protected device. The most accurate monitor remains the threshold voltage and the most sensitive configuration is found to be short hot electron injections in PMOSFET’s. The ability of very short hot electron injections to reveal charging damage is even more evidenced in thinner oxides and the better sensitivity of PMOSFET is explained in terms of conditions encountered by the device during the charging process step