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

利用等离子体-气体凝聚-团束沉积装置制备了锡/硅和银/硅复合纳米颗粒组装膜。透射电子显微镜图像显示，单个纳米颗粒具有复合形态。它们的电阻率在6.1K以下(12at%Si)表现出超导转变的开始。Tc的增加归因于激子型超导电性。还测量了超导临界磁场Hc，发现其高于块体的临界磁场。Ag/Si纳米颗粒组装膜的电导率服从Ag浓度PAg的幂规律。在Pag=Pc附近的剧烈变化表明，银纳米颗粒的渗流发生在阈值Pc处。此外，我们还发现最接近pc的Ag/Si纳米颗粒组装膜在T=5K时的霍尔系数|RH|比体相Ag的霍尔系数高20倍。

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.