PiFM and PiF-IR are the next generation of infrared spectroscopy techniques. PiFM revolutionized atomic force microscopy by providing hemical mapping capabilities. PiF-IR is PiFM’s sister technique used for measuring nanoscale spectra. However, PiF-IR is not just a companion nanoscale IR technique. It is an extremely capable spectroscopy technique that expands the horizons for all types of IR spectroscopy, including FTIR. As reliable and as versatile as FTIR spectroscopy is, it can no longer keep up with the spatial resolution and surface-sensitivity requirements of modern nanomanufacturing. The future needs extremely precise and sensitive analysis, and no other infrared spectroscopy technique can provide the same results as PiF-IR.
FTIR (Fourier transform infrared) spectroscopy is a very well-known analytical technique that is used to detect and identify organic and inorganic molecules. It can effectively analyze solids, liquids, and gases. However, for comparison with PiF-IR, this discussion will be limited to solid materials.
FTIR instruments are typically spectrometers only. That means they offer a simple bulk measurement of the sample without preserving the spatial chemical heterogeneity. Unfortunately, this doesn’t work very well on composite materials. Therefore, some companies couple an infrared microscope to an FTIR spectrometer which can be used to spatially resolve the chemical features in a sample. While this offers an improvement, FTIR is still limited to a spatial resolution of ~5 microns due to the diffraction limit of infrared light. Therefore, unless the sample is available in large quantities of pure material, the utility of FTIR can be limited.
PiF-IR is an AFM-IR technique that uses photo-induced forces (PiF) to analyze solid and thin-film samples at very high spatial resolution. AFM-IR instruments are based on atomic force microscopes, which inherently have a spatial resolution of a few nanometers. When infrared capabilities are added to such an instrument, the leap in spatial resolution and surface sensitivity is astounding. PiFM absorption maps can show chemical distributions with a lateral resolution better than 5 nm, and PiF-IR nanoscale spectroscopy can probe a volume that is at least one billion times smaller than FTIR. Therefore, measurements using these techniques are orders of magnitude more sensitive and localized than the best FTIR microscopes.
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