単分散サイズクラスターの気相合成と基板上での連結・融合過程

抄録

Cluster-assembling is superior in nano-scale-structure control, where we have to make clusters regular in size to draw out the size-dependent characteristics. Using a plasma-gas-condensation type cluster deposition apparatus, we have succeeded in preparing monodispersed transition metal clusters with the mean sizes d=5 to 15nm. We carried out measurement of a transmission electron microscopy and electrical resistivity for clusters randomly deposited on a substrate. The cluster assembling process is interpreted in terms of the percolation theory. The critical percolation thickness, t_c, increases with increasing d, while the critical coverage rate estimated from t_c is 0.63, being independent of d. t_c also increases with increasing the substrate temperature owing to the surface migration of clusters on the substrate. The electrical resistivity and transmission electron microscope image demonstrate the cluster-cluster coalescence above 500K.