Bucky Balls - Buckyballs Explored

The first transistors to be fashioned from a single "buckyball" - a molecule of carbon-60 - have been reported by scientists with the Lawrence Berkeley National Laboratory (Berkeley Lab).

Taking advantage of a phenomenon that is largely viewed as a problem by the electronics industry, the team of Berkeley Lab and UC Berkeley researchers created a separation between two gold electrodes that was about one nanometer (one billionth of a meter) across. This tiny gap could accommodate the insertion of a single buckyball in order to create a molecular-sized electronic device.

"Nature long ago solved the problem of making electronic devices on a molecular-scale and we're now beginning to learn how to do things the way Nature does," says Paul McEuen, a physicist who holds joint appointments with Berkeley Lab's Materials Sciences Division, and with UC Berkeley's Physics Department.

McEuen was one of the co-authors of a paper in the journal Nature (September 7, 2000) that described this research. The other authors were Hongkun Park, Jiwoong Park, Andrew Lim, Erik Anderson, and Paul Alivisatos.

The ability to use individual molecules as functional electronic devices is a much coveted prize in the computer industry because of the potential for dramatically shrinking the silicon-based microelectronic systems of today. As electronic devices are reduced in size to a nanometer scale, the atoms with which silicon must be doped will eventually begin to move about, resulting in poor or uneven performances. Nanoscale sizes should not pose a problem for devices based on single large molecules of carbon as the atoms in these molecules are covalently bonded and therefore firmly locked in place.

Within the past few years, a number of research groups, including McEuen's, have made transistors from carbon nanotubes - tiny sheets of graphite that have been curled and connected along the seam. Although considered a single molecule of carbon, these elongated tubes were several times larger than the soccer-ball shaped carbon-60 molecules used by McEuen and his colleagues to make their newest transistors. Buckyballs are so tiny that, as transistors, they only permit one electron at a time to move through them. This opens the door to the study of single-electron transport effects.

"Transport measurements of these single carbon-60 transistors provide evidence for coupling between the center-of-mass motion of the carbon-60 and single-electron hopping, a novel conduction mechanism that has not been observed in previous quantum-dot studies," the authors stated in their Nature paper. "The transport measurements demonstrate that single-electron tunneling events can be used both to excite and probe the motion of a molecule."