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Film-growth process of hydrogenated amorphous silicon-oxygen alloys (a-SiO:H) from C[O.sub.2]/(C[O.sub.2] + Si[H.sub.4]) plasma has been investigated to control the optoelectronic properties in the resulting materials. Optical emission spectroscopy results and simple simulation results for steady-state density of chemical species in the plasma indicate that main film-growth precursors for a-SiO:H are Si[H.sub.3], OH, and O. Si dangling-bond defect density is drastically increased in a-SiO:H when increasing the C[O.sub.2] gas ratio in C[O.sub.2]/(C[O.sub.2] + Si[H.sub.4]) plasma, being caused by the increase in the contribution ratio of Si-related short-lifetime species (Si[H.sub.x], x < 2) to film growth owing to a severe Si[H.sub.4]-molecule depletion because of high-rate consumption reaction of Si[H.sub.4] with O produced from C[O.sub.2] in the plasma. Considering the primary electron impact dissociation reactions of source gas molecules and several secondary chemical reactions in the plasma, the guiding principle for obtaining high quality a- SiO:H has been proposed. PACS Nos.: 81.05.Gc, 81.15.Gh, 68.55.Ln. Nous etudions le mecanisme de croissance des films d'alliage de silicium-oxygene hydrogene amorphe (a-SiO:H) a partir d'un plasma de C[O.sub.2]/(C[O.sub.2]+Si[H.sub.4]), afin de controler les proprietes optoelectroniques des echantillons qui en resultent. Des resultats de spectroscopie par emission optique et des simulations simples pour des densites stationnaires des elements chimiques dans le plasma, indiquent que les precurseurs principaux des films de a- SiO:H sont Si[H.sub.3], OH, et O. La densite de defauts de liaisons ouvertes augmente dramatiquement dans le a-SiO:H lorsque que le rapport de C[O.sub.2] gazeux augmente dans le plasma de C[O.sub.2]/(C[O.sub.2]+Si[H.sub.4]). Ceci est cause par une augmentation du rapport de contribution a la croissance, des film des especes chimiques de court temps de vie reliees a Si (Si[H.sub.x], x < 2), qui, elle, fait suite un appauvrissement severe en molecules de Si[H.sub.4], lui-meme cause par le haut taux de reaction de Si[H.sub.4] avec O qui est produit dans le plasma a partir de C[O.sub.2]. Considerant l'importance des reactions de dissociation par impact electronique des molecules du gaz source et de plusieurs reactions chimiques secondaires dans le plasma, nous proposons un guide de pratique pour obtenir des films de a-SiO:H de haute qualite. [Traduit par la Redaction], 1. Introduction Control of optoelectronic properties in wide gap materials is one of the key issues for improving the photovoltaic performance of Si-based thin-film solar cells. Hydrogenated amorphous silicon-oxygen alloys [...]

Chloride is used as conservative tracers to estimate hydrological pathways. Field data on treatment of municipal solid waste (MSW) leachate show that Cl is reduced in aerobic treatment. Here laboratory experiments simulating MSW leachate treatment are conducted to see if electrical conductivity (EC) reduction can be duplicated in the laboratory, and to find probable chemical or physical factors explaining EC and chloride reduction. The experiments include three leachate, eight artificial, and three control samples. Mean reduction of EC in the respirometers was 17% for the leachate and 25% in the artificial samples. There was close to zero reduction in the controls. Mean reduction of chloride was 45% in the artificial samples and 9% in the controls. The oxygen consumption was lower in the leachate samples during aeration, probably due to inhibitory compounds. There was no reduction in EC after chemical coagulation with A1 and organic coagulants, 31% reduction in the aerobic system, and 46% in the anaerobic system. Total organic carbon significantly influenced the oxygen consumption. The reduction of chloride and EC depended on the acidity (pH) of the leachate. Centrifugation showed an effect on EC and chloride concentration. Based on these results it seems that the reduction of chloride in leachate treatment depends on the formation of organic precipitates. DOI: 10.1061/(ASCE)0733-9372(2007)133:6(659) CE Database subject headings: Conductivity; Chlorides; Leaching; Municipal wastes; Aerobic treatment.