Visible to Mid-IR Spectromicroscopy with Top-Down Illumination and Nanoscale (≈10 nm) Resolution

Photothermal induced resonance (PTIR), an atomic force microscopy (AFM) analogue of IR spectroscopy also known as AFM-IR, is capable of nanoscale lateral resolution and finds broad applications in biology and materials science. Here, the spectral range of a top-illumination PTIR setup operating in contact-mode expanded for the first time to the visible and near-IR spectral ranges. The result is a tool that yields absorption spectra and maps of electronic and vibrational features with spatial resolution down to approximate to 10 nm. In addition to the improved resolution, the setup enables light-polarization-dependent PTIR experiments in the visible and near-IR ranges for the first time. While previous PTIR implementations in the visible used total internal reflection illumination requiring challenging sample preparations on an optically transparent prism, the top illumination used here greatly simplifies sample preparation and will foster a broad application of this method.

Automated summary

Photothermal induced resonance (PTIR) is an atomic force microscopy method that offers nanoscale lateral resolution and is widely used in biology and materials science. This study demonstrates the expansion of the PTIR setup to the visible and near-IR spectral ranges, allowing for improved resolution and light-polarization-dependent experiments.