Conductivity of macromolecular networks measured by electrostatic force microscopy

High-resolution electrostatic force microscopy (EFM)-phase measurements are reported on molecular networks of semiconductor polymer poly-hexylthiophene (P3HT) and DNA molecules. A lateral resolution of better than 20 nm is demonstrated in EFM-phase images of the P3HT network by detecting the phase shift of the tip along the molecules under electrical bias. Strands of λ-DNA are shown to be highly insulating in comparison to the semiconductor polymer P3HT, with a minimum resistance of ∼1×107 Ω cm.