Nanorods gain gold tips

Researchers from Hebrew University in Israel have devised a way to cause semiconductor nanocrystals and tiny amounts of gold to self-assemble into nanoscale dumbbells, chains and tetrapods.

The rods and tetrapods could eventually serve as ultra-small transistors, memory elements, light-emitting elements and sensors in nanoelectronic and optoelectronic circuitry, according to the researchers. The researchers' semiconductor-gold dumbbells, chain links and tetrapods range from 20 to 40 nanometers in length. A nanometer is one millionth of a millimeter, or the size of a row of 10 hydrogen atoms.

The ability to grow gold tips on nanoscale bits of semiconductor is a significant step toward solving the difficult manufacturing problem of how to wire such small objects together.

The gold tips are bonded to the semiconductor covalently, meaning the gold and semiconductor atoms share one or more electrons; this provides a good electrical contact. The gold provides natural anchor points for connecting semiconductors to electrodes and for self-assembly.

The chemical process the researchers used to bind the gold tips to the semiconductors was fairly simple and straightforward, according to the researchers. This concept could be used to fuse nanorods to other metals, including those that are magnetic.

The nanorod-gold objects could also lead to materials with new chemical and optical properties, according to the researchers.

Use of the gold-tipped metal structures in novel self-assembly could happen within five years; practical applications in nanoelectronics and optoelectronics will emerge in five to ten years, according to the researchers. The work appeared in the June 18, 2004 issue of Science.