Morphology Dependence of Raman Properties of Carbon Nanotube Layers Formed on Nanostructured CeO₂ Films

Multiwalled carbon nanotubes (MWCNTs) were deposited from solution phase onto the nanostructured CeO 2 films grown on a sapphire substrate. High-resolution images by scanning electron microscopy showed that MWCNTs laid on the top of CeO 2 islands. Raman shifts of these combinatorial materials showed considerable dependence on the morphology of the underlying CeO 2 nanostructures. Quantum chemical calculations validated the resonant nanotube vibrations, especially for the stationary longitudinal wave at typical surface morphology, as the origin of this unexpected property of the Raman signal. Considering that the CeO 2 surface morphology is fully controlled by the experimental setup of growth, properties of the CNT layers are tunable toward the requirements of practical applications.