Electrical Transport of Single- and Double-Walled Carbon Nanotubes Functionalized with Monovalent Phenyl Groups

We present a comprehensive study on the effect of monovalent functionalization on the electrical properties of carbon nanotubes, and discuss new strategies that combine extensive functionalization with good electrical conductivity. Many individual single- and double-walled carbon nanotubes (SWNTs and DWNTs) were characterized before and after functionalization with 4-bromophenyl grafts, and after defunctionalization by thermal annealing. Functionalization resulted in a reduction of the ON-state current by an order of magnitude or more in both metallic and semiconducting SWNTs. The OFF-state leak current increased by up to three orders of magnitude in semiconducting SWNTs. Graft bonding was reversible with a 770 K vacuum anneal, although some residual damage was left on the nanotube surface. Functionalization of DWNTs affected the outer wall similarly as for SWNTs, while the inner wall was left in pristine state. Functionalized-DWNTs devices can be operated through the inner wall with electrical performance as good as pristine SWNTs.