Garnering attention for high conductivity, nonlinear optical properties, and more, MXenes are water-processable 2D materials that are considered candidates for applications in electromagnetic interference shielding, optoelectronic and photonic devices among others. Herein we investigate the intrinsic and photoexcited conductivity in Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> CT <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> , a MXene with reported high photothermal conversion efficiency. DFT calculations show that hydroxyl and/or fluorine-terminated $\mathrm{Nb}_{2} \mathrm{CT}_{x}\left(\mathrm{~T}_{x}=\mathrm{OH}\right.$ or $\left.\mathrm{F}\right)$ is metallic, in agreement with THz spectroscopy, which reveals the presence of free charge carriers that are highly localized over mesoscopic length scales. Photoexcitation of Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> CT <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> , known to result in rapid heating of the crystal lattice, is found to produce additional free carriers and a transient enhancement of photoconductivity. Most photoexcited carriers decay over the sub-picosecond time scales while a small fraction remain for much longer, sub-nanoseconds, times.
Authors: Andrew M. Fitzgerald, Kateryna Kushnir, Emily Sutherland, Erika Colin‐Ulloa, Tarek El-Melegy, Mary Qin Hassig, J.E. Martı́n, Ken Ngo, Ronald L. Grimm, Joshua R. Uzarski, Michel W. Barsoum, N. Aaron Deskins, Lyubov V. Titova
DOI: https://doi.org/10.1109/irmmw-thz57677.2023.10298923
Publish Year: 2023
