Non-slender MEMS resonators for advanced AFM applications

Abstract

Atomic force microscopy (AFM) took an astonishing development that started from a simple idea and ended at advanced multifrequency methods today. While AFM equipment has generally involved significantly during this development, MEMS resonators with slender beam geometries remain to be a core component in AFM hardware. The focus on this resonator geometry is easy to understand since it facilitates scanning of sample surfaces. Here, we discuss how slight deviations from the standard beam geometry, namely going to plate resonators with finite width, make additional vibrational modes available for dynamic AFM. Going beyond standard beam geometries requires novel methods for modelling the interaction between resonators and fluid environment [1]. Using these methods, we show that the use of plate resonators has the potential of improving AFM in liquids in terms of the resonator’s quality factor [2]. However, non-conventional resonator geometries lead not only to modified quality factors. The fluid-structure interaction also couples different vibrational modes with important implications to both single- and multifrequency AFM. In the linear regime, these coupling can also be exploited for fluid sensing. In the nonlinear regime, modal couplings allow for implementing sideband cooling or noise squeezing methods [3].