Polarization-modulated rectification at ferroelectric surfaces*

By correlating room temperature conductive atomic force microscopy (c-AFM) with low temperature electrostatic force microscopy (EFM) images taken at different temperatures but the same location, we demonstrate that nanoscale electric conduction between a sharp tip and the surface of ferroelectric HoMnO$_3$ is intrinsically modulated by the polarization of ferroelectric domains. Conductance spectra reveal that the electric conduction is described by polarization-induced Schottky-like rectification at low bias, but dominated by a space-charge limited conduction mechanism at high bias. Our observation demonstrates visualization ferroelectric domain structure by electric conduction, which may be used for non-destructive read-out of nanoscale ferroelectric memories or sensors.