Uniform patterned growth of carbon nanotubes without surface carbon

In order to utilize the unique properties of carbon nanotubes in microelectronic devices, it is necessary to develop a technology which enables high yield, uniform, and preferential growth of perfectly aligned nanotubes. We demonstrate such a technology by using plasma-enhanced chemical-vapor deposition (PECVD) of carbon nanotubes. By patterning the nickel catalyst, we have deposited uniform arrays of nanotubes and single free-standing aligned nanotubes at precise locations. In the PECVD process, however, detrimental amorphous carbon $\mathrm{(a-}\mathrm{C})$ is also deposited over regions of the substrate surface where the catalyst is absent. Here, we show, using depth-resolved Auger electron spectroscopy, that by employing a suitable deposition (acetylene, ${\mathrm{C}}_{\mathrm{2}}{\mathrm{H}}_{\mathrm{2}})$ to etching (ammonia, ${\mathrm{NH}}_{\mathrm{3}})$ gas ratio, it is possible to obtain nanotube growth without the presence of $\mathrm{a-}\mathrm{C}$ on the substrate surface.