Quantitative analysis of nanoscale electrical properties of CNT/PVDF nanocomposites by current sensing AFM†
Quantitative current sensing atomic force microscopy (CS-AFM) is used to characterize the nanoscale electrical properties of carbon nanotube/polyvinylidene fluoride (CNT/PVDF) nanocomposites made with two different CNTs – undoped CNT and N-doped CNT. The conducting domains on the surface connected via a percolating pathway were mapped as a function of applied electrical potential. The conducting domain size and fractal analyses assigned an interconnected aggregate model to the percolating network with the low resistive conducting domain radii ranging from 140–400 nm. These measurements compared well with those determined from bulk measurements for both undoped and N-doped nanocomposites. Significant differences between conductivities determined by CS-AFM and bulk measurements were noted. This difference in conductivity was attributed to challenges in measuring low currents at low applied potential and current saturation issues at high applied potential. For 3.5 wt% undoped CNT/PVDF nanocomposite, the fractional surface area contributing to current increased from 20% at 1 V to 60% at 10 V highlighting the distinct ability to map the distribution of conducting domains with varying resistance, which was not possible to determine through bulk conductivity measurements.