Dynamic observation of carbon nanotube growth on isolated catalyst nanoparticles

Arizona State University, Scottsdale AZ

Investigators

Abstract

Abstract Proposal Title: Dynamic Observation of Carbon Nanotube Growth on Isolated Catalysts Nanoparticles Proposal Number: CTS-0625340 Principal Investigator: Renu Sharma Institution: Arizona State University Analysis (rationale for decision): This proposal will investigate a two-step process to synthesize carbon nanotubes having specific targeted structures and properties. Both of these steps are unique and will contribute to a wider scientific understanding of carbon nanotube synthesis. In the first step, a custom catalyst will be prepared in situ using an electron beam induced deposition (EBID) nanolithographic method. The custom EBID-fabricated catalysts, with particles carefully placed at the edges of holes in a SiO2 film, will allow unobstructed views of the dynamical events leading to nucleation and growth of nanotubes during the second step. The in situ nucleation and dynamic growth of carbon nanotubes via chemical vapor decomposition (CVD) of acetylene over the catalyst particles will be observed. A high-resolution (< 0.2 nm) controlled environment (scanning) transmission electron microscope (ESTEM) will be used for these studies. In addition nanodiffraction data from sub-nanometer regions of the nanotubes and particles will be obtained, as well as compositional and electronic information by electron energy loss spectroscopy. The effect of catalyst particle size and reaction temperature and pressure on nanotube structure will be determined. Growth mechanisms will then be modeled using ab initio methods, with detailed attention paid to the catalyst/nanotube interactions. The topologies of individual nanotubes and their defect structures will also be modeled. The ability to control the fabrication of nanotubes will be an important step towards the broader goal of using them to building circuits or sensor boards. The methods developed in this project can also be used for designing other nanoscale devices. For example, electron beam induced depositions can be used to fabricate arrays of quantum dots. Combinatorial catalysis characterization techniques developed in this research will also be useful for studying catalysis at the atomic level at typical reaction temperatures, with possible implications for the design of other catalysts. The videos showing growth mechanisms, combined with models, form invaluable visual aids for undergraduate nanotechnology education as well as for the Arizona State K-12 outreach program. The principal investigator has been a role model as a successful scientist from an underrepresented group for the undergraduate program at ASU.