Size and load dependence of nanoscale electric contact resistance

Nanoscale electrical resistance between a platinum-coated atomic force microscope tip and highly oriented pyrolytic graphite surface is measured as a function of normal load and tip radius. These measurements are complemented by molecular dynamics simulations that relate load and radius to contact area. Simulation-predicted contact area and experimentally-measured resistance are used to calculate contact resistivity. The results show that the effect of load on resistance can be captured by the real contact area, while tip size, although in part captured by area, affects contact resistivity itself, potentially through interface distance. Our study provides new insight into the effect of load and geometry on nanoscale electric contact and, more significantly, highlights the role of atomic-scale contact features in determining contact resistance.