Field emission properties of single-walled carbon nanotube with amphoteric doping by encapsulation of TTF and TCNQ

Reaction of single-walled carbon nanotubes (SWNTs) with molecules having large electron affinity and small ionization energy achieved p-type (TCNQ : tetracyanoquinodimethane) and n-type (TTF : tetrathiafulvalene) doping, respectively. Encapsulation of those molecules was carried out inside nanotube under vacuum environment. Doping changed the field emission (FE) property by charge transfer between the encapsulated molecules and SWNTs. Optical characterization (near-IR, Raman spectrum) and electric property (conductivity) revealed that charge transfer between SWNTs and molecules starts at certain critical energies. We observed electron density change of SWNTs by optical spectroscopy and conductivity measurement experiment under vacuum. XPS experiments revealed that the encapsulated molecules have strong interaction with SWNTs.