Expanding AFM Capabilities by Multifrequency AFM

Abstract

By the introduction of multifrequency AFM in 2004, surface characterization by AFM has expanded to compositional mapping and subsurface visualization of soft matters. In this talk, the newly developed techniques to improve the current dynamic modes of AFM with the focus of multifrequency AFM measurements on soft matters in ambient air and liquid environments will be discussed. Secondly a new methodology, known as trimodal AFM, for mechanically characterizing the subsurface of soft samples, allowing users to gradually, controllably and reversibly reveal features that are buried under the surface are explained. Based on the current findings of our research, an experimental protocol to select excitation frequency in air for single tapping mode and bimodal AFM are presented. Additionally, a rigorous guideline for the selection of drive frequency in ambient air, liquid environment based on the energy quantities and slope of the cantilever’s phase response is discussed. Finally, an advantage of using higher eigenmodes for imaging soft matters has been proposed and verified experimentally. Such a control over higher eigenmodes give the capability to the experimentalist to modulate the sensitivity of the cantilever’s dynamics to tip-sample forces. By having the capability to modulate the sensitivity of the cantilever, AFM imaging and characterization capabilities are expanded from imaging the surface of nano-bubbles to subsurface imaging of polymers.