Imaging and simulation of surface plasmon polaritons on layered 2D MXenes.

Rieger, Janek; Ghosh, Atreyie; Spellberg, Joseph L; Raab, Calvin; Mohan, Aishani; Joshi, Prakriti P; King, Sarah B · Sci Adv · 2025

basic_science · Level V

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Abstract

Two-dimensional (2D) transition metal carbides and nitrides, commonly known as MXenes, are a class of 2D materials with high free carrier densities, making them highly attractive candidates for plasmonic 2D materials. In this study, we use multiphoton photoemission electron microscopy (<i>n</i>P-PEEM) to directly image the plasmonic near fields of multilayers of the prototypical MXene, Ti<sub>3</sub>C<sub>2</sub>T<i><sub>x</sub></i>, with mixed surface terminations (T<i><sub>x</sub></i> = F, O, and OH). Photon-energy dependent <i>n</i>P-PEEM reveals a dispersive surface plasmon polariton between 1.4 and 1.9 electron volts on MXene flakes thicker than 30 nanometers and waveguide modes above 1.9 electron volts. Combining experiments with finite-difference time-domain simulations, we reveal the emergence of a visible surface plasmon polariton in MXenes, opening avenues for exploration of polaritonic phenomena in MXenes in the visible portion of the electromagnetic spectrum.