Carbon nanotubes (CNTs) are an important class of materials with several technological applications because they possess unparalleled properties in terms of ballistic electrical conductivity, thermal conductivity, tensile strength, and sensitivity to chemical and biological agents. To exploit these properties in functional devices, a major barrier that must be addressed is the ability to control important properties such as diameter, chirality, quality, density, and alignment. There is also the need to reduce the growth temperatures of CNTs (below 400°C) to enable growth on a variety of sensitive, pre-functionalized substrates, thereby making the growth process compatible with current nanofabrication technology. This talk focuses on the development of a suitable catalytic template for the controlled growth of single-wall carbon nanotubes (SWNTs) by plasma-enhanced CVD. An amine-terminated fourth-generation poly (amidoamine) (PAMAM) dendrimer with numerous reactive functional groups has been used as carriers to deliver nearly monodispersed Fe2O3 nanoparticles (3.2 ±1nm) on different substrates. Microwave PECVD growth with these Fe2O3 nanoparticles supported on Al2O3 substrates and annealed in an N2 ambient result in enhanced SWNT selectivity, quality and diameter uniformity. The application of dc bias voltage during SWNT growth seems to selectively remove amorphous carbon and metallic SWNTs, leaving mainly large-diameter semi-conducting SWNTs. Using these catalyst nanoparticles; a shielded growth approach has been developed for the growth of CNTs at low temperatures (200-400°C). Postmortem characterization of the catalytic template by XPS has provided insights into the growth mechanism of CNTs.
Birck Nanotechnology Center, Room 1001