Behavior of a movable electrode in piezo-response mode of an atomic force microscope

Abstract

The objective of this work was to understand the effect of the movable electrode (the tip of an atomic force microscope) on a piezoelectric-induced (PEI) image. Local polarization is induced on a lead zirconate titanate (PZT) thin film using an atomic force microscope (AFM), by applying dc voltage between the movable electrode and the Pt bottom electrode. The polarized PZT film is then characterized by the AFM using a two-pass method, in which both the topography and PEI image are obtained. The surface morphology is recorded in the first pass under contact mode with a fixed setpoint. A PEI image is obtained in the second pass in piezo-response mode. In this mode, the sample surface is scanned by applying ac voltage between the AFM tip and the Pt bottom electrode at sample displacement. PEI images of various sample displacement, corresponding to different stress exerted by the tip on the sample surface, are obtained and analyzed using force–sample displacement curves. It is found that PEI images can be detected if the tip adheres to the sample. The asymmetry of the A cos θ signal is improved as the force changes from repulsive to attractive.