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.