Preparation of Catalytic Nanoparticles in Mesoporous Silica Film for Oriented Growth of Single-Walled Carbon Nanotubes

Vertically oriented single-walled carbon nanotubes (SWNTs) attract considerable attention, because it is expected as an ideal field emitter that can realize lower threshold voltage and higher electric current than microtips of Si or metals. In this study, we aim that SWNTs are vertically oriented using mesoporous silica film as a guide of the growth for SWNTs. For the orientation, the catalyst for the growth must be attached to the substrate. Three kinds of catalyst loading methods are examined here. The first one is an impregnation method; the calcined mesoporous silica film is immersed in solution of cobalt acetate and iron acetate. The second one is an incorporation method; mesoporous silica film is prepared using Co/Fe-doped silica sol solution. The third one is a sputtering method; the mesoporous silica film is coated on the cobalt thin film deposited by sputtering. From these investigations, it is concluded that the mesoporous silica film prevents agglomeration of Co catalyst, resulting in the formation of oriented SWNTs from the bottom of the silica mesopores.