Hierarchically Organized Carbon Nanotube Arrays from Self-Assembled Block Copolymer Nanotemplates

The ideal 1D structure of carbon nanotubes (CNTs) lends them various attractive properties such as tunable conductivity, extremely high electron mobility, and large charge storage capacity. Owing to their molecular scale dimensions and unique electronic properties, CNTs are considered to be promising building blocks for future nanoelectronics devices, and are attractive candidates for overcoming the fundamental limitations of conventional Si-based microdevices. CNTs need to be integrated within device architectures for nanoelectronics applications. However, the development of a robust large-scale organization process for assembling CNTs remains a formidable challenge. For applications such as field emission and nanoelectronics, it is necessary to grow vertically oriented CNTs having desired properties at predetermined locations. Of the various synthetic approaches for growing CNTs, chemical vapor deposition (CVD), which is a facile and easily scalable process, is the most widely used method for the vertical growth of CNTs. In a typical CVD experiment, metal particles on a substrate surface catalyze the vertical growth of CNTs. As a consequence, the diameter and position of the obtained individual CNTs are determined by the size and lateral distribution of the catalyst particles. Catalyst particles for the vertical growth of CNTs are generally prepared by the deposition and heat treatment of a thin metal catalyst film on a substrate. The deposited film dewets to form catalyst nanoparticles upon the heat treatment process. However, the prepared catalyst particles are usually polydisperse in size and randomly distributed over the substrate surface. The application of lithographic patterning processes may lead to a narrower size distribution and relatively uniform lateral distribution of catalyst particles, but the intrinsic resolution limit of conventional photolithography processes implies that it is impossible to controllably