Visualization of anisotropic conductance in polydiacetylene crystal by dual-probe frequency-modulation atomic force microscopy/Kelvin-probe force microscopy

Abstract

The authors recently developed a dual-probe atomic force microscope (DP-AFM) system as a powerful measurement or fabrication tool in the fields of nanoelectronics and nanobiology. In this study, they performed frequency-modulation Kelvin-probe force microscopy (FM-KFM) experiments on a polydiacetylene (PDA) single crystal using the DP-AFM system. While a bias voltage was locally applied to the PDA surface with one probe, the surface potential on the surrounding area was mapped with the other probe by FM-KFM. The surface potential images showed anisotropic distributions, which are explained by the anisotropic conductance of the PDA crystal due to the quasi-one-dimensional electronic band structure along the diacetylene main chain. They also discuss the mechanisms of charge injection from a probe to the PDA crystal and the difference in the anisotropic conductance ratio for electrons and holes.