Experimental Study On The Assembly And Contact Resistance Of Nano Functional Carbon Materials

As representatives of nano-functional carbon materials,carbon nanotubes(CNTs)and graphene have great application potentials in nano sensor,field effect transistor,micromechanics,energy storage,and composites,among others.Integrating CNTs and graphene into micro-and nano-devices is a critical step for applying them in many fields.CNTs and graphene can be assembled by dielectrophoresis(DEP)without damage and pollution.As a promising way,DEP has been frequently used for this purpose.The high contact resistance of CNTs and graphene is an important factor influencing the performance of CNT-and graphene-based devices.Reducing the contact resistance should be put into the first step.As a simple and common way,high temperature annealing and local joule heating(applying electricity)have significant effects on reducing the contact resistance without harsh external conditions.First,we assembled graphene by DEP and investigated the influence of the DEP process parameters including the magnitude of the applied voltage,the concentration of the graphene suspension,and the duration of the electric field.Results show that the quantity of the assembled graphene increases with increasing these parameter values,and the concentration of the graphene suspension is the most significant factor.The optimal parameter combination of assembly is 3V,4?g/m L,120 s.Second,the effects of high temperature annealing and local joule heating on reducing the contact resistance of CNTs were investigated by using orthogonal experiment design and variance analysis,and the optimal parameter combinations for reducing the contact resistance are 300?,15 min,20?/min and 120?W,1KHz,180 s.Results show that the annealing temperature and the power are the leading factors causing the reduction of the resistance.Finally,we compared the effect and the stability of high temperature annealing with local joule heating when reducing the contact resistance of graphene,and draw the conclusion that the former is more effective to reduce the contact resistance than the latter,the resistance was reduced by 92.82%.But the latter is more stability than the former,the resistance returned only by 4.80%.