Carbon nanotube transistor: Doping and ambipolarity

Pure carbon nanotubes have been known to exhibit ambipolarity. This is very different from the conventional semiconductors that are controlled by an intentional doping with extrinsic materials. The ambipolarity has been a serious drawback in adopting carbon nanotubes for CMOS technology. Carbon nanotubes show p-type behavior in ambient conditions. The difficulty arises from the absence of stable n-type dopants in ambient conditions. A series of chemical approaches have been done in our group to search for n-type dopants. NADH and viologen molecules have demonstrated successfully to show n-type behavior by donating electrons to nanotubesand furthermore show high stability in ambient conditions.[1-5] In addition to these approaches, we will also demonstrate a way of utilizing ambipolarity of nanotuibes without such intentional dopings that ambipolarity is in fact advantageous in fabricating CMOS inverter and logic circuits.