Bundles of carbon nanotubes grown on sapphire and quartz substrates by catalytic hot filament chemical vapor deposition

Carbon nanotubes were deposited on non-conductive optically transparent sapphire substrates of various crystallographic orientations and on amorphous quartz glass. The substrates were covered by catalysts in which trivalent iron, Fe(III), was the dominant component. The nanotubes were synthesized by catalytic hot filament chemical vapor deposition. During their production, they form bundles composed of multiwalled carbon nanotubes and have a length of up to several tens of micrometers, thickness between 1 and 4 μm, and a non-circular cross-section. The growth of these bundles on a non-porous non-conducting optically transparent substrate was confirmed by scanning electron microscopy and by Raman spectroscopy.