Amphoteric and Controllable Doping of Carbon Nanotubes by Encapsulation of Organic and Organometallic Molecules

By using first principles calculations, we show that fine tuning of both $p$- and $n$-type doping can be realized on single-wall carbon nanotubes (SWNTs) by tuning the electron affinity or ionization potential of the organic and organometallic molecules encapsulated inside SWNTs. This novel type of SWNT-based material offers great promise for molecular electronics because of its air stability, synthetic simplicity and the abundance of organic and organometallic molecules.

Figure 1

Total energies $\Delta E$ of organic- and organometallic molecule doped (16,0) SWNTs as a function of the off-axis displacement $r$, with $\Delta E(r=0)$ used as a reference.

Figure 2

Geometric structures of organic- and organometallic molecule doped (16,0) SWNTs. Pink ball: C; white ball: H; blue ball: N; green ball: F; yellow ball: S; black ball: cobalt. The arrows represent the shift directions of the organic- and organometallic molecules that are used to determine the $\Delta E\mathrm{\text{−}}r$ relation of Fig. 1.

Figure 3

Electronic band structure of the (16,0) SWNT doped by organic- and organometallic molecules, with $E_f=0$. Bigger $\alpha$-, $\beta$, and $\gamma$ bandwidths than shown in this figure are expected if the random orientations of the organic- and organometallic molecules are taken into account.