Probing Nanoscale Electromechanical Behaviors of Relaxor Ferroelectrics in Highly Conductive Liquid Environments

We perform electromechanical imaging with improved resolution by piezoresponse force microscopy on a biocompatible relaxor ferroelectric crystal in conductive liquid environments. The nanoscale domain wall and characteristic domain pattern in NaCl solutions of up to almost 0.1M can be clearly detected. The unique insulated nanoelectrode tip of scanning probe microscopy has been applied to overcome traditional limitations of electrical investigation in aqueous environments by efficiently sensing local electrical signals. Unlike the good insulation of air or vacuum environments, the electromigration of ions in electrolytes corresponding to the applied electric field forms a double-layer structure, which screens the electric potential distributions near the biased tip and sample surface. Systematical numerical simulations of the Debye screening effect near the tip-electrolyte and sample-electrolyte interfaces give intuitive clarifications on the physical natures and help formulate strategies to improve electromechanical probing in a liquid environment with high conductivity.