Researchers at the Georgia Institute of Technology in Atlanta have created a new type of nanometer-scale structure that may be used in inexpensive ultra-small sensors, flat-panel displays, and other electrical nanodevices. Termed "nanobelts," these thin, flat structures are composed of transparent semiconducting metal oxides.
While the bulk of one-dimensional nanoscale research has centered on carbon nanotubes, nanobelts may hold promise for a wider variety of applications. Nanobelts have been created from oxides of zinc, tin, indium, cadmium, and gallium. They have ribbon-like structures and narrow, rectangular cross sections. Researchers project that other semiconducting oxides may be used to create nanobelts in the future.
According to the researchers, these nanobelts offer significant advantages over nanowires and carbon nanotubes. With clean surfaces that do not require protection against oxidation, the nanobelts are chemically pure. They're also structurally uniform and nearly defect free. Each is composed of one crystal with specific surface planes. The uniform structure of these devices may enable the mass production of nanoscale electronic and optoelectronic devices.
To produce the nanobelts, commercially available metal-oxide powders are placed in the center of an alumina tube. As argon or nitrogen gas flows through the tube, the tube is heated to between 1100°C and 1400°C. The powders evaporate and then form the nanobelts by solidifying on an alumina plate in a cooler portion of the furnace.
As oxides, nanobelts do not require cleaning or handling in special environments, unlike nanowires, which must be prevented from oxidizing. The surfaces of nanobelts are automatically sharp and clean. As flexible structures, the nanobelts can be bent 180° without breaking. While the typical width of the structures is between 30 and 300 nm, their thickness ranges from 10 to 15 nm. Most measure up to hundreds of microns long, but some have been produced as long as several millimeters.
Though nanobelts don't have the high structural strength intrinsic to cylindrical carbon nanotubes, their uniformity suits electronic and optoelectronic applications. Also, the production of carbon nanotubes lacks the control to yield massive volumes of high-purity, defect-free structures with uniform properties.
The researchers say nanobelt production can be controlled to create high volumes of nearly defect-free structures. This is important because defects can destroy quantum mechanical transport properties in nanowire-like structures.
The research effort is headed by Zhong Lin Wang, director of the Center for Nanoscience and Nanotechnology at Georgia Tech. Further research is being conducted to investigate the nanobelts' optical, electrical, and surface characteristics. For details, visit www.gatech.edu.