Modeling the near-field interaction in s-SNOM in the mid-infrared to terahertz ranges

• Grant number: 24/04695-8
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Effective date (Start): May 01, 2024
• Effective date (End): April 30, 2025
• Field of knowledge: Physical Sciences and Mathematics - Physics - Condensed Matter Physics
• Principal Investigator: Raul de Oliveira Freitas
• Grantee: Victor Mazzotti Almeida
• Host Institution: Centro Nacional de Pesquisa em Energia e Materiais (CNPEM). Ministério da Ciência, Tecnologia e Inovação (Brasil). Campinas , SP, Brazil
• Associated research grant: 19/14017-9 - From excitons waves to THz-phonons: 2Ds materials nano-optics via synchrotron infrared nanospectroscopy, AP.JP

Abstract

The rise of near-field nanoscopy techniques has unlocked the comprehension of previously inaccessible physical phenomena compared to traditional far-field microscopy. Central to this advancement is scattering near-field scanning microscopy (s-SNOM), a method enabling the investigation of light-matter interactions in nanoscale regions (up to 10 nm) of materials. s-SNOM has propelled nanophotonics research, particularly in exploring collective excitations like optical phonon resonances in polar crystals and plasmonic resonances in graphene and semiconductors. Despite its contributions, the theoretical understanding of near-field interactions remains a focal point for the global scientific community due to its complexity. s-SNOM differs from conventional techniques by incorporating a metallized atomic force microscope (AFM) tip, mediating the near-field interaction with the sample. Analyzing this tip-sample system is challenging due to intrinsic parameters such as tip geometry, composition, excitation wavelength, and sample composition. Various phenomenological models have been proposed, with a focus on interpreting the AFM tip's geometry, often as a sphere dipole, ellipsoid, or hyperboloid. While these models show efficacy in specific cases, especially in the mid-infrared range, modeling complex tip-sample systems often requires numerical approaches using simulation software like COMSOL and LUMERICAL, demanding expertise and computational resources.