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Eoghan Dillon1 Anirban Roy1 Curtis Marcott2 Craig Prater1

1, Anasys Instruments, Santa Barbara, California, United States
2, Light Light Solutions, LLC, Seabrook Island, South Carolina, United States

Infrared microspectroscopy is a powerful technique for obtaining unique chemical information from a variety of biological systems. In general, spatial resolutions are limited by the Abbe diffraction laws to ~ λ/2 (3-10 µm). In recent years, the development of the AFM-IR technique has allowed for overcoming these diffraction limitations by using an AFM probe as the detector for IR absorption. Using a quantum cascade IR laser (QCL), the molecular vibrations in a sample are excited, leading to thermal expansion of the surface, which is monitored using an AFM cantilever. This technique reduced the spatial resolution of < 10 nm, however, in certain cases this high resolution is not required and the size of an image in AFM-IR is limited by the piezo stage to sub 100 µm. A new technique has been developed that fills the gap between IR microspectroscopy and AFM-IR. This is an optical based technique that still beaks the diffraction limits associated with conventional IR microspectroscopy, and provides sub-micron spatial resolution. Taking advantage of the same fundamental principles that govern AFM-IR, the thermal expansion of a sample surface induced by a QCL IR laser is monitored using a visible probe laser, instead of an AFM probe. This unique technique provides transmission like IR spectra while operating in a reflective regime. The spatial resolution is limited by the diffraction limit of the visible probe laser, while also being independent of the IR wavelength used. In this talk we will focus on the combination of this new optical probe based IR technique with AFM-IR to fully characterize a variety of materials, from the micro scale to the nanoscale using the same QCL laser source.

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