Smaller, faster and less expensive electronic devices may be on the horizon if carbon nanotubes could replace silicon that is widely used in circuit boards today. Researchers at the University of Illinois at Urbana-Champaign may have come up with just the right solution to make this a feasible idea.
They claim to have found a way to purify arrays of single-walled carbon nanotubes (SWCNTs) of any metallic character. With such a process, when these nanotubes are arranged in films, some of them take on the properties of metals rather than semiconductors, leading to the shorting of the concerned circuit.
A single bad tube out of 100000 is enough to destroy an electronic device. This calls for a very strict quality control regimen since the purity of the series must be higher than 99.999 percent. The University of Illinois team managed to find a workaround to the issue in form of a coating of organic material.
The trick is to lay a coat of organic material on an array of carbon nanotubes in contact with a sheet of metal. The next step is to apply a current to the sheet in order to reveal the tubes playing the part of metal conductors instead of semiconductors. The metal nanotubes get heated up by the current.
This results in a thermal capillary flow that opens up a trench in the organic topcoat above the series of carbon nanotubes, says AIP. Thus exposed, the tubes which are technically metallic contaminants, can be extracted using a standard benchtop instrument, while the organic topcoat may later be rinsed off.
What’s left behind is an electronic wafer layered with semiconducting carbon nanotubes that meet the kind of quality benchmark needed to build circuits. Such tubes are highly attractive because they are minuscule down to an atomic scale and greatly shrink the possible size of an electronic switch.