Secret Lives of Carbon Nanotubes

The recent advent of transmission electron microscopes with integrated scanning probe microscope sample stages is permitting unprecedented nanoscale observation and analysis of materials. Jianyu Huang of Sandia National Laboratories, for example, uses this technology to study simultaneously the electrical and mechanical properties of carbon nanotubes. He anchors a multiwall carbon nanotube between the stage base and probe tip and then runs an electrical current through the tube to heat it to a particular temperature -- and may also use the tip to stretch the tube -- all while continuously recording electrical and force measurements and taking a transmission electron microscope snapshot every few seconds.

At the AVS 55th International Symposium & Exhibition, Huang will describe how he stitched together the transmission electron microscope images of a single-wall nanotube growing within the core cavity of a multiwall nanotubes. The resulting short time-lapse video clearly reveals the answer to a long-standing carbon nanotube question: During their formation, the free end of a growing nanotube is a closed cap, not an open tube. (Nanotube pioneer Sumio Iijima in Japan has also recently achieved a similar result.) Understanding the growth mechanism is essential in creating nanotubes with the desired structure, or chirality, required for devices such as field-effect transistors.

In earlier work, Huang has used the same technology to observe unexpected plastic deformation of stretched carbon nanotubes and the creation of closed-shell buckyballs within multiwall carbon nanotubes. His collaborators at Rice University have modeled the data and explained how conventional dislocation principles can be modified to explain the observed behavior in nanotubes.

Huang's talk, "In-Situ Electron Microscopy Enabled by a TEM-SPM Platform" will be held at 2:40 p.m. on Thursday, October 23, 2008, in Room 310 of the Hynes Convention Center.

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