A
field emission device having bundles of aligned parallel carbon nanotubes on a substrate. The carbon nanotubes are oriented perpendicular to the substrate. The
carbon nanotube bundles may be up to 300 microns tall, for example. The bundles of carbon nanotubes extend only from regions of the substrate patterned with a catalyst material. Preferably, the catalyst material is
iron oxide. The substrate is preferably
porous silicon, as this produces the highest quality, most well-aligned nanotubes. Smooth, nonporous
silicon or
quartz can also be used as the substrate. The method of the invention starts with forming a
porous layer on a
silicon substrate by
electrochemical etching. Then, a
thin layer of iron is deposited on the
porous layer in patterned regions. The iron is then oxidized into
iron oxide, and then the substrate is exposed to
ethylene gas at elevated temperature. The
iron oxide catalyzes the formation of bundles of aligned parallel carbon nanotubes which grow perpendicular to the
substrate surface. The height of the
nanotube bundles above the substrate is determined by the duration of the
catalysis step. The
nanotube bundles only grow from the patterned regions.