We present Si nanotubes prepared by reductive decomposition of a silicon precursor in an alumina template and etching. These nanotubes show impressive results, which shows very high reversible charge capacity of 3247 mA h/g with Coulombic efficiency of 89%, and also demonstrate superior capacity retention even at 5C rate (=15 A/g). Furthermore, the capacity in a Li-ion full cell consisting of a cathode of LiCoO2 and anode of Si nanotubes demonstrates a 10 times higher capacity than commercially available graphite even after 200 cycles.

Ultrathin silicon nitride films prepared by combining rapid thermal nitridation with lowpressure chemical vapor deposition Appl.Stability of hydrogen in silicon nitride films deposited by lowpressure and plasma enhanced chemical vapor deposition techniques J. Vac. Sci. Technol. B 7, 150 (1989); 10.1116/1.584707Hopping conduction in undoped lowpressure chemically vapor deposited polycrystalline silicon films in relation to the film deposition conditionsThe effect of stress in silicon nitride films, deposited by the low-pressure chemical vapor deposition process, on the point defect concentrations in silicon has been studied. The stress level in the nitride film is varied by controlling the ratio offiow rates of reactant gases R = fSiII,ClJfNH" from 1/6 to 6. The stress in the nitride film is tensile and its magnitude increases with decreasing R. During anneals at 1100 °C in Ar with a high stress in the nitride, phosphorus diffusion in silicon is retarded, antimony diffusion is enhanced, and extrinsic stacking faults shrink faster than with a low stress. These results suggest that a vacancy supersaturation and a self-interstitia! undersaturation exist under the nitride and that the deviation from the equilibrium point defect concentrations are closely related to the stress level in the silicon nitride film. From the phosphorus junction profiles with varying shape width, an effective vacancy diffusivity of 3 X 10 -10 eml/s has been obtained.

Literature values for the diffusivity of the silicon interstitial or interstitialcy, I, range over several orders of magnitude and have activation energies between 1 and 4 eV. We propose a model for bulk trapping effects on the I diffusivity which provides a consistent explanation for the observed discrepancies. It reconciles the effects of different materials (float-zone, Czochralski, and epitaxial silicon) and processes (diffusion and gettering) on the apparent value of the I diffusivity. New experimental results which directly indicate substantial bulk effects in different types of silicon support the validity of the model.