Researchers are working to identify materials that could one day replace silicon to make computing faster. Sambandamurthy Ganapathy, Sarbajit Banerjee, and their colleagues at the University of Buffalo have found a vanadium oxide bronze whose unusual electrical properties in nanowire form, including unprecedented metal–insulator transitions, could increase the speed at which information is transferred and stored.
In the August 17 online edition of Advanced Functional Materials (DOI: 10.1002/adfm.201201513), the researchers report that they have synthesized single-crystalline β-PbxV2O5 nanowires from vanadium oxide and lead. When exposed to an applied voltage near room temperature, the nanowires transform from insulators to metals that more readily conduct electricity. Each of these two states—insulator and metal—could stand for a 0 or 1 in the binary code that computers use to encode information, or for the “on” and “off” states that the machines use to make calculations.
“The ability to electrically switch these nanomaterials between the on and off state repeatedly and at faster speeds makes them useful for computing,” said Ganapathy.
“Silicon computing technology is running up against some fundamental road blocks, including switching speeds,” said Banerjee. “The voltage-induced phase transition in the material we created provides a way to make that switch at a higher speed.”
As with other nanomaterials, the health and environmental impacts of the nanowires would have to be investigated before their widespread use, especially since they contain lead, Banerjee said. One intriguing characteristic of the material they synthesized is that it only exhibits valuable electrical properties in nanoform. That is because nanomaterials often have fewer defects than their bulkier counterparts.
The distinctive structure in these nanowires is crucial to their ability to switch from an insulator to a metal. Specifically, in the insulator phase, the position of the lead in the nanowires’ crystalline structure induces pools of electrons to gather at designated locations. Upon applying a voltage, these pools join together, allowing electricity to flow freely through them and transforming the material into a metal.
“When materials are grown in bulk, there’s a lot of defects in the crystals, and you don’t see these interesting properties,” said Peter Marley who is lead author. “But when you grow them on a nanoscale, you’re left with a more pristine material.”
