Far-field extraction of the dielectric function of exfoliated flakes near phonon resonances

Far-field extraction of the dielectric function of exfoliated flakes near phonon resonances | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Far-field extraction of the dielectric function of exfoliated flakes near phonon resonances Mitradeep Sarkar, Michael T. Enders, Mehrdad Shokooh‐Saremi, Evgenia Klironomou, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7037943/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 11 You are reading this latest preprint version Abstract The lateral dimensions of flakes of emerging low-dimensional materials that are mechanically exfoliated do not typically exceed some tens of micrometers. This prohibits the experimental extraction of their complex dielectric function (ϵ(ω)) at mid-infrared (IR) frequencies with conventional angle-resolved spectroscopic ellipsometry due to the large size of an IR beam that exceeds a flake’s size. To circumvent this challenge, previous approaches relied on mapping the dispersion of surface phonon polaritons using near-field scanning probes. These, however, involve expensive instrumentation, are sensitive to external conditions, require significant numerical fitting and become cumbersome in the presence of optical anisotropies and strong spatial dispersion. We introduce a simple empirical method to extract the in-plane components of the dielectric tensor of small-sized flakes using conventional Fourier Transform Infrared (FTIR) micro-spectrometry. By detecting minima in reflectance spectra near a phonon resonance, we obtain ϵ per frequency without fitting to any a priori known model. To recover ϵ(ω) over an extended spectral range, we apply this method to multiple flakes of various thicknesses, which are often available onto the same substrate upon exfoliation. Physical sciences/Materials science Physical sciences/Optics and photonics Physical sciences/Physics dielectric function phonon polaritons Spectroscopic Ellipsometry Fourier Transform Infrared Spectroscopy Full Text Additional Declarations No competing interests reported. Supplementary Files SupplementaryExtractionarticlef02072025.pdf Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 02 Sep, 2025 Reviews received at journal 31 Aug, 2025 Reviews received at journal 30 Jul, 2025 Reviews received at journal 21 Jul, 2025 Reviewers agreed at journal 15 Jul, 2025 Reviewers agreed at journal 14 Jul, 2025 Reviewers agreed at journal 14 Jul, 2025 Reviewers invited by journal 14 Jul, 2025 Editor assigned by journal 10 Jul, 2025 Submission checks completed at journal 04 Jul, 2025 First submitted to journal 03 Jul, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7037943","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":485503350,"identity":"580c8cef-4c0a-4482-815f-53595d581b73","order_by":0,"name":"Mitradeep Sarkar","email":"","orcid":"","institution":"Institute of Photonic Sciences","correspondingAuthor":false,"prefix":"","firstName":"Mitradeep","middleName":"","lastName":"Sarkar","suffix":""},{"id":485503352,"identity":"e91bccd8-afad-48f9-8cc1-120def683820","order_by":1,"name":"Michael T. 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