Co cluster coalescence behavior observed by electrical conduction and transmission electron microscopy

We deposited monodispersed Co clusters with mean diameters d = 6, 8.5, and 13 nm on quartz and microgrid substrates using a plasma-gas-condensation-ty pe cluster beam deposition system. The cluster-cluster coalescence behavior of the Co cluster assemblies was investigated by in situ electrical conduc tivity measurements and ex situ transmission electron microscopy (TEM). The electrical conductivity measurement indicates that, below temperature T ap proximate to 100 degreesC, the Co clusters with d=8.5 nm maintain their ori ginal size as deposited at room temperature, while the cluster-cluster coal escence takes place at their interface at T > 100 degreesC. The TEM observa tion indicates that the morphology of the cluster distribution shows no mar ked change at substrate temperatures T-s < 250 degreesC. Above T-s = 300 de greesC, the interfacial area of coalesced clusters is crystalline, and has its own orientation, different from that of two connected cluster cores. (C ) 2001 American Institute of Physics.