Effects of a carbon nanotube layer on electrical contact resistance between copper substrates

Reduction of contact resistance is demonstrated at Cu-Cu interfaces using a multiwalled carbon nanotube (MWCNT) layer as an electrically conductive interfacial material. The MWCNTs 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 a Cu-MWCNT-Cu interface as a function of probe position. For an apparent contact area of 0.31 mm(2), 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 this arrangement as a small-scale force sensor. Also, the Cu-MWCNT-Cu interface was roughly two times stiffer than the bare Cu-Cu interface. Contact area enlargement and van der Waals interactions are identified as important contributors to the contact resistance reduction and stiffness increase. A model based on compaction of the MWCNT layer is presented and found to be capable of predicting resistance change over the range of measured force.