APPLICATIONS OF TECHNOLOGY:

Researcher, Alex Zettl, shown here with a model of a carbon nanotube, has made ball bearings and mechanical switches far too small to be seen without the aid of an electron microscope.

• Electronic devices (Schottky barriers, PN junctions, resistors)
• Microswitches
• Micromachines
• Microsensors
• Computation elements
• High-strength fibers
• Electronically, mechanically or thermally controlled catalysts
• Ingredients in "smart materials" (e.g. crack self-sensing materials)

ABSTRACT:

Alex Zettl, Vincent Crespi, Marvin Cohen and Steven Louie at Berkeley Lab have designed carbon nanotube structures that enable the creation of nanometer-scale diodes, transistors and sensors. These carbon nanotubes, containing metal/semiconductor or semiconductor/semiconductor junctions, may be used to form electronic devices which are 1-2 nanometers in each dimension. Nanoscale devices envisioned include Schottky barriers, quantum wells and transistors 10,000 times smaller in area than present commercial silicon devices.

A novel topological solution that matches tubes with different electronic structures enables the creation of these junctions. Carbon nanotubes are synthesized to contain pentagon-heptagon pair defects in their normal hexagonal structure. The defects change the helicity of the nanotube and alter its electronic structure. In addition to forming all carbon heterojunctions, the tubes can be doped with boron or nitrogen to add charge carriers to the semiconducting region.