Tapping mode atomic force microscopy in liquid with an insulated piezoelectric microactuator

Abstract

Tapping mode atomic force microscopy in liquids is enhanced using an insulated cantilever with an integrated piezoelectric microactuator. When vibrating the cantilever via direct force modulation by the actuator, a single resonance peak appears in the plot of rms cantilever amplitude versus excitation frequency, eliminating the spurious resonances typical of acoustic excitation in a liquid medium. This simplifies selection of the cantilever’s natural resonance frequency for improved tuning accuracy and speed. Acoustic excitation can excite cantilever modes that do not displace the tip of the cantilever but vibrate the microscope’s detection system and create unwanted liquid-coupled acoustic waves between the liquid-cell and the sample. These modes are eliminated by directly forcing the cantilever. Insulated microactuated probes offer a simple and more direct alternative solution to recently presented magnetic tuning methods.