Physics of nanoscale spectral imaging beyond diffraction limit
Wednesday, January 28, 2026;
121 Earth & Engineering Science Building
335PM-425PM
Speaker: Slava Rotkin from ESM
Abstract: Recent success in synthesis of new two-dimensional materials (2DM) beyond graphene (including TMDCs, heteronanotubes, hBN family, MXenes and atomic polar metals), was followed by a large number of works exploring their properties and seeking for novel applications in quantum technologies, biosensing, energy and computing. Atomically thin 2DMs have an ultimate surface-to-volume ratio. While it helps biosensing, electronics and other applications, surface non-uniformities may drastically increase variability of materials properties. Such non-uniformities are known to be a critical limiting factor for other types of nanomaterials as well. Modulation of optical properties at the nanometer scale due to atomic impurities or adsorbates or defects, wrinkles or ruptures, lattice mismatch, doping and work function variation is important to be able to control. However, even before developing synthetic approach to mitigate the problem, appropriate characterization tools are needed to detect such a modulation.
In this talk, several methods for nanoscale (sub-diffractional) optical characterization will be presented. Correlated multiplexed (multidimensional) optical imaging technique will be introduced using a few examples including: a vertical heterostructure comprised of monolayer graphene and single layer flakes of MoS2,[1] heteronanotubes with carbon core and hBN/MoS2 shell,[2] glass nanoindentations[3,9] and heterostructures of graphene/Ag/SiC atomic layers[4,10]. The correlation of several information channels (including microRaman[5,6]) allows one to obtain information on, e.g., local Fermi level and strain tensor components[1] or distribution of chemical bonds in a glassy material[3].
It will be shown that similar results could be obtained using scattering Scanning Near-field Optical Microscopy (sSNOM), the technique which produces multidimensional information in a single run. sSNOM will be shown to map polaritonic wavefunction and detect polaritonic confinement in heterostructures of atomic-thin metals[10]. As the time allows, a quantum theory of sSNOM imaging will be discussed [7,8].
Literature:
1. ACS Nano 2022, 16, 2598.
2. ACS Nano 2021, 15, 5600.
3. Acta Materialia 2021, 208, 116694.
4. Science Advances 2025, 11, eadw1800.
5. Nature Comm 2015, 6, 8429.
6. J Mat Chem B 2017, 5, 6536.
7. ACS Nano 2015, 20, 360.
8. S.V. Rotkin, Materials Science & Technology 2022 (October 9-13, Pittsburgh, PA).
9. Ceramics International 2024, 50 Part A, 32457.
10. X. Li, et.al, (submitted).
Bio:
Slava V. Rotkin is Frontier Professor of Engineering Science & Mechanics at Penn State University. He received MSc in Optoelectronics from Electrotechnical University and Ph.D. in Physics & Mathematics at Ioffe Institute (St. Petersburg, Russia). Rotkin is an editor of 3 books and author of 190 papers and proceedings. Most recently, his work is focused on near-field optics and plasmonics, nano-biophysics, and 2D quantum materials. Rotkin mentored 30+ graduate students, 10+ postdoctoral fellows, 60+ undergraduates and a dozen of high-school students. Rotkin is recipient of several scientific awards, including Fellow of the Electrochemical Society, The Fulbright-Nehru Academic and Professional Excellence Award, The Japan Society for the Promotion of Science Fellowship, the Japan Gateway: Kyoto University Distinguished Professor, Hillman Award, Class of '68 Fellowship, Libsch Early Career Research Award, Feigl Junior Faculty Chair, and Beckman Fellowship
Hosted by: Lana Fulton, lub18@psu.edu
