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Local structure and effective chemical valency of Mn impurity atoms incorporated in wide-band-gap (Ga,Mn)N epilayers have been investigated by using x-ray absorption fine structure techniques. The x-ray results provide direct evidence for the substitution of majority Mn atoms for the Ga sites in GaN, with an effective valency close to Mn(II), up to a rather high Mn concentration about 2 at. %. A small fraction of the impurity atoms could also form Mn clusters.

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Silicon (Si) is considered to be the most promising anode material to replace graphite due to its higher theoretical capacity. Nanotechnology has played an important role in addressing the serious volume changes that occur during the lithium process of Si anode removal. However, the development of Si anodes has not yet reached the industry standard for the next generation of commercial lithium-ion batteries. Nowadays, with the increasing requirements for battery energy density in diverse industries, the use of silicon anode materials to increase energy density, co-utilization of Si, graphite, new binders, and electrolytes has become a commercially viable method to achieve high energy. Therefore, in this review, we emphasize the necessity of using Si/graphite anodes, new binders, and electrolytes at the same time in commercialization and carefully review the development of Si/graphite anodes. The typical Si anode mixed graphite electrode is discussed, and various strategies for constructing Si/graphite composite materials are organized according to their synthesis method. It is particularly noteworthy that we systematically introduce the key factors for the co-utilization of Si/graphite anodes, new binders, and electrolytes. Finally, some suggestions on the practical application of Si/graphite anodes are given.

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Local structures around Mn in In 1Ϫx Mn x As films grown by molecular-beam epitaxy have been studied by using Mn K-edge extended x-ray-absorption fine-structure ͑EXAFS͒ technique. Substitution of Mn atoms for the In sites is found in samples either grown at low substrate temperatures ͑near 200°C͒ or with a low Mn concentration ͑about 1 at. %͒. This result represents a significant extension of an earlier EXAFS study and serves as direct experimental evidence for III-V diluted magnetic semiconductors obtained by substitutional doping of Mn impurities in InAs.

Pronounced structure in x-ray excited luminescence (XEL) has been observed in dilute Tb-doped Y2O3 (Y2O3:Tb) nanocrystals. This effect affords a means to assess different energy transfer mechanisms in the nanocrystals and also an opportunity for novel device applications. Sharp jumps and oscillations are found in the XEL output with the incident x-ray energy around the absorption edges of Y and Tb. When compared with a bulk Y2O3:Tb sample, these effects are attributed to some unique electronic and optical properties of doped nanocrystals related to quantum confinement of charge carriers, and the main features can be explained by a proposed model of multichannel energy transfer. Extended x-ray absorption fine structure techniques have also been employed to study the effect of size variation and chemical doping on the local structures in Y2O3 and Y2O3:Tb nanocrystals. The local environment surrounding Y and Tb in the nanocrystals is compared with that in the respective bulk material. The results indicate that Tb impurity atoms substitute for Y sites in bulk Y2O3, while doping in the nanocrystals is complicated by the large fraction of surface atoms and local disorder.