Wikipedia
AFM-IR (atomic force microscope infrared-spectroscopy) is one of a family of techniques that are derived from a combination of two parent instrumental techniques; Infrared spectroscopy and Scanning probe microscopy (SPM). The term was first used to denote a method that combined a tuneable Free electron laser with an Atomic force microscope (a type of SPM) equipped with a sharp probe that measured the local absorption of infrared light by a sample; it required that the sample be coupled to an infrared-transparent prism and be less than 1μm thick. It improved the spatial resolution of photothermal AFM-based techniques from microns to circa 100 nm.
Recording the amount of infrared absorption as a function of wavelength or wavenumber creates an infrared absorption spectra that can be used to chemically characterize and even identify unknown materials. Recording the infrared absorption as a function of position can be used to create chemical composition maps that show the spatial distribution of different chemical components. Novel extensions of the original AFM-IR technique and earlier techniques have enabled the development of bench-top devices capable of nanometer spatial resolution, that do not require a prism and can work with thicker samples, and thereby greatly improving ease of use and expanding the range of samples that can be analysed. One of these techniques has achieved spatial resolutions down to around 20 nm, with a sensitivity down to the scale of molecular monolayer
AFM-IR is related to techniques such as Tip-enhanced Raman spectroscopy (TERS) and Scanning near-field optical microscopy (SNOM), and other methods of vibrational analysis with scanning probe microscopy.