Crystal structure tunes nanowires

Several groups of researchers are working to control the growth of wires that can be as narrow as a few atoms in diameter and that can be used as nanoscale electronic components. Researchers have been able to grow nanowires that have specific material compositions, and at specific positions and orientations.

Researchers from the University of California at Berkeley and Lawrence Berkeley National Laboratory have added a new dimension to making nanowires. They have found a way to control the crystal structure of nanowires made from the semiconductor materials gallium nitride and zinc oxide.

The process promises to enable electronic components like light-emitting diodes and laser diodes that have tunable properties, according to the researchers.

Crystals have a lattice structure, and depositing a thin layer of a material on a crystal surface causes the material to adopt the crystal structure of the surface. The researchers were able to coax nanowires to grow with a particular crystal orientation by matching the lattice of the surface crystal with the desired structure of the nanowire.

The researchers used the method to grow nanowires 15 to 40 nanometers in diameter. One crystal structure contained nanowires with a triangular cross-section, and a second type had a hexagonal cross-section.

This type of control is key to making useful components from nanowires. The researchers found that that gallium nitride nanowires grown with different crystal structures emit light at different wavelengths.

Nanowires could be used in practical miniaturized ultraviolet light sources in two to five years, according to the researchers. The work appeared in the July 25, 2004 issue of Nature.