Controlled growth of CNT in mesoporous AAO through optimized conditions for membrane preparation and CVD operation.

Anodic aluminum oxide (RAAO) membranes with a mesoporous structure were prepd. under strictly controlling exptl. process conditions, and phys. and chem. characterized by a wide range of exptl. techniques. Com. anodic aluminum oxide (CAAO) membranes were also investigated for comparison. We demonstrated that RAAO membranes have lower content of both water and phosphorus and showed better porosity shape than CAAO. The RAAO membranes were used for template growth of carbon nanotubes (CNT) inside its pores by ethylene chem. vapor deposition (CVD) in the absence of a catalyst. A composite material, contg. one nanotube for each channel, having the same length as the membrane thickness and an external diam. close to the diam. of the membrane holes, was obtained. Yield, selectivity and quality of CNTs in terms of diam., length and arrangement (i.e. no. of tubes for each channel) were optimized by investigating the effect of changing the exptl. conditions for the CVD process. We showed that upon thermal treatment RAAO membranes were made up of crystd. allotropic alumina phases, which govern the subsequent CNT growth, because of their catalytic activity, likely due to their Lewis acidity. The strict control of exptl. conditions for membrane prepn. and CNT growth allowed us to enhance the carbon structural order, which is a crit. requisite for CNT application as a substitute for copper in novel nano-interconnects.