Photoexcited Charge Carrier Dynamics and Electronic Properties of Two-dimensional MXene, Nb2CTx

Authors

Andrew M. Fitzgerald, Department of Physics, Worcester Polytechnic Institute, Worcester, MA, USA
Emily Sutherland, Department of Physics, Worcester Polytechnic Institute, Worcester, MA, USA
Tarek A. Elmelegy, The British University in EgyptFollow
Mary Qin Hassig, Department of Materials Science and Engineering, Drexel University, Philadelphia, PA, USA
Julia Martin, Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, MA, USA
Erika Colin-Ulloa, Department of Physics, Worcester Polytechnic Institute, Worcester, MA, USA
Ken Ngo, US Army DEVCOM Soldier Center, Natick, MA, USA
Ronald L. Grimm, Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, MA, USA
Joshua R. Uzarski, US Army DEVCOM Soldier Center, Natick, MA, USA
Michel W. Barsoum, Department of Materials Science and Engineering, Drexel University, Philadelphia, PA, USA
N. Aaron Deskins, Department of Chemical Engineering, Worcester Polytechnic Institute, Worcester, MA, USA
Lyubov V. Titova, Department of Physics, Worcester Polytechnic Institute, Worcester, MA, USA
Kateryna Kushnir Friedman, Department of Physics, Worcester Polytechnic Institute, Worcester, MA, USA

Document Type

Article

Publication Date

2024

Abstract

Two-dimensional, 2D, niobium carbide MXene, Nb2CTx, has attracted attention due to its extraordinarily high photothermal conversion efficiency that has applications ranging from medicine, for tumor ablation, to solar energy conversion. Here, we characterize its electronic properties and investigate the ultrafast dynamics of its photoexcitations with a goal of shedding light onto the origins of its unique properties. Through density functional theory, DFT, calculations, we find that Nb2CTx is metallic, with a small but finite density of states at the Fermi level for all experimentally relevant terminations of Nb2CTx that can be achieved using HF or molten salt etching of the parent MAX phase, including –OH, –O, –F, –Cl, –Br, –I. In agreement with this prediction, THz spectroscopy reveals an intrinsic long-range conductivity of ~ 60 Ω-1 cm-1, with significant charge carrier localization and a charge carrier density (~1020 cm-3) comparable to Mo-based MXenes. Excitation with 800 nm pulses results in a rapid enhancement in photoconductivity, which decays to less than 25% of its peak value within several picoseconds, underlying the efficient photothermal conversion. At the same time, a small fraction of photoinjected excess carriers persists for hundreds of picoseconds, and can potentially be utilized in photocatalysis or other energy conversion applications.

Recommended Citation

Fitzgerald, Andrew M.; Sutherland, Emily; Elmelegy, Tarek A.; Hassig, Mary Qin; Martin, Julia; Colin-Ulloa, Erika; Ngo, Ken; L. Grimm, Ronald; Uzarski, Joshua R.; Barsoum, Michel W.; Deskins, N. Aaron; Titova, Lyubov V.; and Friedman, Kateryna Kushnir, "Photoexcited Charge Carrier Dynamics and Electronic Properties of Two-dimensional MXene, Nb2CTx" (2024). Mechanical Engineering. 69.
https://buescholar.bue.edu.eg/mech_eng/69