(Invited) Multi-Frequency Atomic Force Microscopy for Nanoscale Infrared Spectroscopy

Abstract

The emergence of tools at the forefront of advanced atomic force microscopy (AFM) holds great potential to bolster our fundamental understanding of heterogeneous and dynamic systems at the nanoscale, of prime interest for material science, chemistry and life sciences. Developments using multi-frequency AFM provide more sensitive detection and a wider frequency span to explore the morphology, mechanical and chemical properties of the sample volume. However how these performances compare to more conventional modes is not well established.Here, we will present the implementation of multifrequency AFM nanoscale infrared imaging and spectroscopy. We will first discuss how the nonlinear nature of the tip-sample interaction in AFM can be used as a sensitive channel to access infrared (IR) fingerprints of materials at the nanoscale. We will compare the IR signatures obtained with conventional nanoscale IR spectroscopy, both on homogeneous and heterogeneous materials. In doing so, we will estimate the volume probed as a function of the data acquisition parameters and materials properties. Finally, we will illustrate how the high sensitivity and spatial resolution of nanoscale IR spectroscopy provide new insights in the molecular arrangements of complex systems, especially when guided by macro- and micro-scale studies.