Optical signature of charge transfer in n-type carbon nanotube transistors doped with printable organic molecules

Single-walled carbon nanotubes (SWCNTs) are known to be p-type semiconductors, due to unintentional hole doping. Therefore, air-stable electron dopants are important for the fabrication of logic circuits. Recently, n-type characteristics of SWCNT film transistors have been achieved by using several types of donative organic molecules, and these molecular dopants have opened a route for application. However, it is still unclear whether the cause of n-type operation is the Fermi level shift of SWCNTs or the lowering of the Schottky barrier for electrons. In this study, we found the evidences of electron transfer from organic molecules to SWCNTs using optical measurements.