Experimental Study Of The Effect Of Doping On The Electrical Conductivity Of Carbon Nanotubes

In order to apply CNTs in micro-/nano-electronics,it is essential to reduce the contact resistance of carbon nanotubes(CNTs).Here,low contact resistance between CNTs and metal can be achieved by doping CNTs with transition metal.It is difficult for CNTs without defects and hydrophilic groups to accommodate foreign atoms.In this paper,a systematic study on the technique for producing defects on the surface of CNTs by high temperature heat treatment is conducted.Results show that,high-temperature heat treatment can activate CNTs,and produce defects and oxygencontaining hydrophilic groups carbonyl at the surface and end of CNTs.The Au-doped CNTs are obtained by immersing CNTs in chloroauric acid solution to adsorb chloroauric acid,and by experiencing reduction in hydrogen to obtain Au in the metallic state.The obtained CNTs are characterized,and results show that CNTs are successfully doped with Au and Au is N-type dopants.A study on the technique for activating CNTs by acid treatment is also carried out.Results show that,acid treatment can effectively activate CNTs and produce defects and oxygen-containing hydrophilic groups carboxyl at the surface and end of CNTs.Subsequently,the acid treated CNTs are doped with transition metal Au and are then characterized.Results show that CNTs are successfully doped with Au and contain more Au-doped nanoparticles with more uniformity than those doped with Au after heat treatment.CNT samples are assembled onto a pair of Au electrodes by dielectrophoresis(DEP),and the real-time detection of the contact resistance is achieved by LCR.Results show that the contact resistance between CNTs and Au electrodes have been generally reduced after doping with Au,some even reduce to half of the original value.Compared with the CNTs doped with Au after heat treatment,the contact resistance of CNTs doped with Au after acid treatment is lower.This shows that the acid treatment is a more ideal method to activate CNTs,and doping Au after acid treatment is an effective way to improve the contact resistance of CNTs.