Effects of a carbon nanotube layer on electrical contact resistance between coppersubstrates

Abstract

Reduction of contact resistance is demonstrated at Cu–Cu interfaces using a multiwalledcarbon nanotube (MWCNT) layer as an electrically conductive interfacial material. TheMWCNTs are grown on a copper substrate using plasma enhanced chemical vapour deposition(PECVD) with nickel as the catalyst material, and methane and hydrogen as feed gases.The MWCNTs showed random growth directions and had a bamboo-like structure.Contact resistance and reaction force were measured for a bare Cu–Cu interface and aCu–MWCNT–Cu interface as a function of probe position. For an apparent contact area of0.31 mm2, an 80% reduction in contact resistance was observed when the MWCNT layer was used.Resistance decreased with increasing contact force, thereby making it possible to use thisarrangement as a small-scale force sensor. Also, the Cu–MWCNT–Cu interface was roughlytwo times stiffer than the bare Cu–Cu interface. Contact area enlargement and van derWaals interactions are identified as important contributors to the contact resistancereduction and stiffness increase. A model based on compaction of the MWCNT layer ispresented and found to be capable of predicting resistance change over the range ofmeasured force.