New Hybrid Carbon Nanotubes-Nanowires Could Improve Computer Chips and Sensors

Nanotechnology is in full expansion and carbon nanotubes and metal nanowires are increasingly used in new devices.

Now, a team at Rensselaer Polytechnic Institute has made hybrid structures that combine the properties of carbon nanotubes and metal nanowires, which could improve computer chips, displays, sensors, and many other electronic devices.

Even if conductivity qualities of carbon nanotubes are impressive, methods to attach individual nanotubes to metal contacts have been difficult.

The new technique permits the precise binding of carbon nanotubes to metal pins, allowing the use of carbon nanotubes as interconnections and devices in computer chips. "This technique allows us to bridge different pieces of the nanoelectronics puzzle, taking us a step closer to the realization of nanotube-based electronics," said Fung Suong Ou, a graduate student in materials science and electrical engineering at Rensselaer.

Chip designers are looking for powerful devices, but at the same time, they want to shrink the dimensions of chip components to the nanometer scale. "Carbon nanotubes and nanowires that became available in the 1990s are promising candidates to act as connections at this scale, because they both possess interesting properties", said Ou.

Carbon nanotubes have an amazing mechanical strength, besides being excellent conductors of electricity, producing interconnects that are many times faster than current ones based on copper. "Gold nanowires also have very interesting optical and electrical properties, and they are compatible with biological applications", Ou said. "In order to take full advantage of these materials, we demonstrate the idea of combining them to make the next generation of hybrid nanomaterials", he said. "This approach is a good method to marry the strengths of the two materials."

The metal nanowires are made using an alumina template that can be designed to have pore sizes in the nanometer scale. Copper or gold wires are formed inside the pores, and then the whole device is placed in a furnace, where a carbon-rich material is found. At high temperatures, the carbon atoms arrange themselves along the channel wall of the template and the carbon nanotubes grow directly on top of the copper wires. "It's a really easy technique, and it could be applied to a lot of other materials", Ou said. "The most exciting aspect is that it allows you to manipulate and control the junctions between nanotubes and nanowires over several hundred microns of length. The alumina templates are already mass-produced for use in the filter industry, and the technique can be easily scaled up for industrial use."

The team is currently intending to connect carbon nanotubes to a semiconductor material, which could be employed as a diode.

Photo credit: Rensselaer/Fung Suong Ou. Junction between a gold nanowire (top) and a carbon nanotube.