Carbon nanotube semiconductors augur silicon replacement
Researchers at the University of Maryland (College Park, MD) have found that semiconducting carbon nanotubes offer a mobility 25% higher than other semiconducting material and more than 70% higher than the mobility of silicon. These findings promise to spur the replacement of conventional semiconducting materials with carbon nanotubes in applications ranging from computer chips to biochemical sensors.
The researchers fabricated a nanotube transistor and found that the room-temperature mobility of their nanotube is greater than 100,000 cm2 /V-s at 25°C, breaking the previous record for room-temperature mobility�77,000 cm2 /V-s in indium antimonide�that stood for 48 years. Today's silicon computer chips offer a mobility of approximately 1,500 cm2 /V-s.
Measurements were done on long nanotubes in which metal wires were placed precisely on each one. The nanotubes measured 0.3 mm in length or about 100,000 times their diameter�that is 100 times longer than the ones previously studied.
The nanotubes were grown directly on flat silicon chips. Since it was difficult to locate the nanotubes on the chip in order to connect the wire to them, a special technique using a scanning electron microscope was developed.
Many challenges still exist before nanotubes can replace silicon in computer chips. Researchers need to find a way to control the contact resistance between the nanotubes and metal electrodes. They are also investigating how nanotubes need to be placed with precision on substrates.
For more information, contact Lee Tune of
�Christina Nickolas
Advertisement
