Study on synthesis method for core-shell type cluster and novel functions by the surface and interface effects

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Sn/Si and Ag/Si composite nanoparticle assembled films were prepared by a plasma-gas-condensation cluster beam deposition apparatus. Transmission electron microscope images indicated that individual nanoparticles have composite morphologies. Their electrical resistivity exhibits the onset of superconducting transition below 6.1 K (for 12at%Si). The increased TC is attributable to exciton-type superconductivity. The superconducting critical magnetic fields, Hc, were also measured and found to be higher than the critical magnetic field of the bulk Sn. The electrical conductivity of Ag/Si nanoparticle assembled films obeys a power law of the Ag concentration pAg. The dramatic change at around pAg = pc, indicates that the percolation of Ag nanoparticles takes place at the threshold value pc. Moreover, we found that the Hall-coefficient |RH| at T = 5 K of Ag/Si nanoparticle assembled film with the closest pAg to p¬c is 20 times higher than that of the bulk Ag.