Researchers make nanotube transistors that outperform silicon ones

Researchers at the University of Wisconsin-Madison in the US have developed a way to remove virtually all impurities from carbon nanotube transistors, enabling a higher electrical space current density than in silicon or gallium arsenide transistors.

With their new technique, the researchers were able to produce wafers measuring around 2.5 by 2.5 centimeters. One of the problems with producing transistors from carbon nanotubes, a long-standing candidate to replace silicon, concerns the impurities that occur in the form of contamination with metallic nanoparticles that can cause ‘short circuits’ between the carbon nanotubes.

It is also important to properly position the carbon nanotubes with the correct amount of space between them and to remove the residual solvent after the molding process without changing the position. The researchers were able to remove the polymer used to insulate the semiconducting nanotubes from each other by ‘baking’ the wafers in a vacuum oven. As a result, the researchers obtained good conductivity between the nanotubes and electrodes.

The end result was that the researchers’ transistors only had 0.01 percent metallic contamination left in them. The transistor was able to achieve an electrical space current density 1.9 times that of the “best silicon transistors of today” at a comparable charge, the researchers write in their paper.