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 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 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.
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