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Metastability effects in hydrogenated microcrystalline silicon thin films due to air, high purity nitrogen, helium, argon, and oxygen were investigated using temperature-dependent dark conductivity, photoconductivity, and steady-state photocarrier grating methods. It was found that short-term air, nitrogen, and inert gases caused a small reversible increase of [σ.sub.Dark] and [σ.sub.photo] within a factor of two, but they did not affect the minority carrier μτ-products significantly. These changes are partially reduced by vacuum treatment and completely reduced after heat treatment at 430 K. However, oxygen gas treatment at 80°C resulted in more than an order of magnitude increase in both [σ.sub.Dark] and [σ.sub.photo] and an increase in the diffusion length, [L.sub.D], by 50% from that of the annealed-state value in highly crystalline samples, while no significant metastability is detected in amorphous and low crystalline silicon thin films. A following heat treatment partially recovers both [σ.sub.Dark] and [σ.sub.photo] to their annealed-state values, while [L.sub.D] decreases only slightly. Such increase in the [L.sub.D] values could be due to a decrease in the density of recombination centers for holes below the Fermi level, which may be related to passivation of defects by oxygen on the surface of crystalline grains. PACS Nos.: 73.61.Jc, 73.63.Bd, 73.50.Pz, 72.80.Ng. Nous etudions les effets de la metastabilite dans des films minces de silicium microcristallins hydrogenes du a de l'air, de l'azote tres pur, de l'helium, de l'argon et de l'oxygene, en utilisant la dependance en temperature de la conductivite en obscurite, la photoconductivite et la methode de photocarrier grating en regime stationnaire. Nous trouvons qu'a court terme, l'air, l'azote et les gaz inertes causent de petites augmentations reversibles de [σ.sub.Dark] et [σ.sub.photo] a l'interieur d'un facteur deux, mais n'affectent pas de facon significative les porteurs minoritaires μτ. Ces changements sont partiellement reduits par un traitement par le vide et le sont completement apres chauffage a 430 K. Cependant, le traitement a l'oxygene a 80°C cause une augmentation de plus d'un ordre de grandeur de [σ.sub.Dark] et [σ.sub.photo] et une augmentation de 50 % de la longueur de diffusion [L.sub.D], compare a la valeur d'echantillons cristallins recuits, alors qu'aucune metastabilite n'est detectee dans les films minces de silicium amorphe et faiblement cristallin. Un chauffage subsequent ramene partiellement [σ.sub.Dark] et [σ.sub.photo] a leur valeur de recuit, mais [L.sub.D] ne diminue qu'un peu. Une telle augmentation de [L.sub.D] pourrait etre due a une diminution de la densite des centres de recombinaison sous le niveau de Fermi et peut etre reliee a la passivation des defauts par l'oxygene sur les grains cristallins de la surface. [Traduit par la Redaction], 1. Introduction Hydrogenated microcrystalline silicon (μc-Si:H) has been extensively studied for the last two decades and successfully applied as an absorber layer in thin film silicon solar cells [1, 2]. [...]

We review the material properties that allowed amorphous silicon to become the dominant large area semiconductor and then point out how amorphous oxide semiconductors could displace a-Si in thin film transistors, and how phase change materials, such as GeSbTe alloys, have provided an optical storage technology and will provide a nonvolatile electrical storage technology based on their unique properties. PACS Nos.: 71.15.Mb, 71.23.Cq, 73.61.Jc. Nous passons en revue les proprietes du silicium amorphe qui lui ont permis de devenir un joueur si dominant dans les semi-conducteurs et nous soulignons comment les oxydes de semi-conducteurs amorphes pourraient remplacer a-Si dans les transistors en films minces et comment les materiaux a changement de phase, tel l'alliage GeSbTe, peuvent nous donner une technologie de stockage optique et nous fournir une technologie de stockage electrique non volatile, a cause de leurs uniques proprietes. [Traduit par la Redaction], Introduction This paper reviews the properties and usefulness of amorphous silicon (a-Si) versus other contender amorphous semiconductors over the history of the ICANS conference. Early ICANS conferences focused on the [...]

As silicon-based electronics approach the limit of improvements to performance and capacity through dimensional scaling, attention in the semiconductor field has turned to graphene, a single layer of carbon atoms arranged in a honey-comb lattice. Its high mobility of charge carriers (electrons and holes) could lead to its use in the next generation of high-performance devices. Graphene is unlikely to replace silicon completely, however, because of the poor on/off current ratio resulting from its zero bandgap. But it could be used to improve silicon-based devices, in particular in high-speed electronics and optical modulators., Silicon-based microprocessors and memory chips with a linewidth as small as 20 nm can meet the demand for low-power multifunctional chips that can process and store massive amounts of heterogeneous [...]