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Material Contrasts in s-SNOM and nano-FTIR

Lars Mester key learning objectives: Characterization of Organic Samples with s-SNOM: The talk highlighted the effective use of s-SNOM in studying organic materials. Organic samples, such as polymers, exhibit "weak oscillators" in their dielectric function. These oscillators represent molecular vibrations and can be identified through their unique spectral fingerprints. The speaker emphasized the simplicity and direct correspondence between the near-field response and the material's dielectric function in organic samples. This makes s-SNOM particularly effective for identifying and analyzing organic materials, even at the molecular level. Resonance Phenomena in Strong Oscillators and Phonons: The discussion on strong oscillators and phonons in materials like silicon carbide demonstrated the potential of s-SNOM in exploring resonant phenomena. In such cases, the dielectric function can reach negative values, leading to a significantly enhanced near-field response. This enhancement allows for highly sensitive measurements, such as identifying crystal polymorphs or mapping strain in semiconductors by exploiting phonon resonances. Charge Carrier Dynamics in Inorganic Materials: The talk also covered how s-SNOM can be used to study charge carrier dynamics in inorganic materials. By examining the transition from high to low reflectivity across different frequencies, one can infer the charge carrier concentration in a material. This aspect is particularly relevant for materials with a significant charge carrier response, like semiconductors. The speaker explained that understanding and quantifying this transition is crucial for accurately characterizing such materials with s-SNOM. Overall, the presentation provided a comprehensive overview of the capabilities of s-SNOM in studying a wide range of materials, from organic polymers to inorganic semiconductors, highlighting its versatility in material characterization. This video was recorded with the financial support of the Teaming for Excellence program (European Union Horizon 2020; GA 857543) during the Near-field Optical Nanoscopy Summer School (Donostia- San Sebastian; 6-9 June 2023) organized by neaspec/attocube AG, CIC nanoGUNE BRTA and the ENSEMBLE3 Centre of Excellence.