Uniform patterned growth of carbon nanotubes without surface carbon

In order to utilize the unique properties of carbon nanotubes in microelect ronic devices, it is necessary to develop a technology which enables high y ield, uniform, and preferential growth of perfectly aligned nanotubes. We d emonstrate such a technology by using plasma-enhanced chemical-vapor deposi tion (PECVD) of carbon nanotubes. By patterning the nickel catalyst, we hav e deposited uniform arrays of nanotubes and single free-standing aligned na notubes at precise locations. In the PECVD process, however, detrimental am orphous carbon (a-C) is also deposited over regions of the substrate surfac e where the catalyst is absent. Here, we show, using depth-resolved Auger e lectron spectroscopy, that by employing a suitable deposition (acetylene, C 2H2) to etching (ammonia, NH3) gas ratio, it is possible to obtain nanotube growth without the presence of a-C on the substrate surface. (C) 2001 Amer ican Institute of Physics.