Correlative microscopy and spectroscopy of nanophotonic materials

BIO Web of Conferences 129, 13017 (2024) EMC 2024 https://doi.org/10.1051/bioconf/202412913017 Correlative microscopy and spectroscopy of nanophotonic materials Michael Foltýn1, Petr Liška1, Peter Kepič1, Rastislav Motúz2, Jaroslav Jiruše2, Andrea Konečná1, Vlastimil Křápek1, Tomáš Šikola1, Michal Horák1 1Brno University of Technology, Brno, Czech Republic, 2TESCAN Group, R&D Department, Brno, Czech Republic We present a comprehensive study of nanophotonic materials by correlative electron and optical microscopy and spectroscopy. We focus on a phasechanging material vanadium dioxide, which is relevant for active plasmonics and optical metasurfaces [1], and on lead-halide perovskite (CsPbBr₃) [2]. We performed a comprehensive analysis of a VO₂ nanoparticle and CsPbBr₃ nanocrystals using a combination of analytical transmission electron microscopy and optical methods like ellipsometry and transmission. We have explored the metal-insulator transition (MIT) in the single vanadium dioxide nanoparticle caused by in-situ heating and we have identified the dielectric and the metallic phase of the nanoparticle by imaging, diffraction, electron energy loss spectroscopy, and optical transmission. Our results show that differences in high-resolution images and diffraction patterns obtained at high and low temperatures confirm that MIT is related to a modification of the crystal lattice. In low-loss EELS, the MIT is manifested by the emergence of the plasmon peak in the high-temperature metallic phase. Moreover, we have shown that the transition can be observed directly using imaging techniques such as STEM-ADF and DF-TEM with no need for in-situ spectroscopy. This finding allowed us to study the hysteresis of the MIT in vanadium dioxide with a high spatial resolution. We have observed that the transition from the dielectric to metallic phase is smooth and spans a rather large temperature range while the backward transition is abrupt. Further, we analyzed CsPbBr₃ nanocrystals using correlative microscopy allowing the examination of structural, chemical, and optical properties from identical areas. Moreover, the use of 4D-STEM in a FIB/SEM allowed us to determine the crystallographic orientation of individual nanoparticles. Our results show that their stoichiometry is uniform and independent of their morphology. The photoluminescence peak emission energy is dependent on the dimensions of nanocrystals, with a blue shift up to 9 nm in wavelength with a decreasing size due to the confinement effect [2]. To conclude, our results provide a comprehensive analysis of the MIT in the single vanadium dioxide nanoparticle and pave the way to phase-changing devices made of vanadium dioxide. Further, we have shown that our CsPbBr₃ nanocrystals are of high quality, exhibiting bright and size-tunable PL emission [3]. © The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0 (https://creativecommons.org/licenses/by/4.0/). BIO Web of Conferences 129, 13017 (2024) EMC 2024 https://doi.org/10.1051/bioconf/202412913017 Keywords: vanadium dioxide; nanoparticles; EELS; 4D-STEM Reference: 1. P Kepič et al., ACS Photonics 8 (2021), p. 1048. https://doi.org/10.1021/acsphotonics.1c00222 2. P Liška et al., J. Phys. Chem. C 127 (2023), p. 12404. https://doi.org/10.1021/acs.jpcc.3c03056 3. This research is supported by TAČR (FW06010396) and GAČR (22-04859S). 2  (...truncated)