Direct nanoscale conductivity measurements of surface tracking on epoxy nanocomposites

Conductive Atomic Force Microscopy (C-AFM) was used to investigate if conductive by-products exist within surface tracks—closely related to electrical trees—that are generated by high-power surface flashover events on epoxy nanocomposites used in high-breakdown dielectric applications. Here, we show that topography measurements alone are insufficient to identify conductive surface tracks unambiguously. Instead, by mapping DC currents flowing into the sample from the scanned C-AFM tip, conductive tracks up to three orders of magnitude less resistive than adjacent epoxy nanocomposite material are revealed. Ohmic behavior was confirmed by systematically incrementing the applied voltage, thereby providing a unique method for directly quantifying and mapping the conductivity in electrical breakdown-induced surface tracks, with potential for future applications to the investigation of bulk electrical trees.