Dual-Frequency Peak Force Photothermal Microscopy for Simultaneously Spatial Mapping Chemical Distributions and Energy Dissipation

Abstract

Deciphering correlations between physical properties at the nanoscale requires multimodal measurement with high spatial resolution at the nanometer scale. One platform to achieve multimodal imaging is through scanning probe microscopy. In this article, we report the development of dual-frequency peak force photothermal microscopy, which is a multimodal atomic force microscopy (AFM)-based spectroscopic imaging method. The method delivers simultaneous infrared and visible nanoscopy within one AFM scan frame, mapping the distribution of chemical components from infrared absorption and photothermal responses from electronic transitions. We apply this new method to organic–inorganic perovskite photovoltaics material, revealing chemical distributions at the surface and detecting localized heat generation. In addition, we observe that the photothermal heat generation appears at the back side of the light illumination direction due to local optical field distributions around nanoscale grains. As a measurement tool, dual-frequency peak force photothermal microscopy is expected to facilitate the characterizations of novel photovoltaic materials through correlative mapping of chemicals and optical absorption properties.

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