Journal article
Terahertz Spectroscopy of Intrinsic and Photoexcited Carrier Dynamics in Ti₂CTx MXene Films
2d materials, v 13(3), Forthcoming
11 Jul 2026
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Abstract
Metallic MXenes hold strong potential for applications in flexible electronics, electromagnetic interference shielding, photonics, and photothermal energy conversion. Realizing these applications requires a detailed understanding of carrier transport and its response to optical excitation. Here, we use terahertz (THz) time-domain spectroscopy (THz-TDS) and THz time-resolved spectroscopy (TRTS) to investigate the intrinsic conductivity and ultrafast photoresponse of Ti₂CTₓ MXene, a less-explored member of the MXene family. Analysis of the complex THz conductivity spectra suggests that oxidation fragments Ti₂CTₓ flakes into small, conductive regions separated by non-conductive areas. Within these conductive regions, electrons exhibit scattering times and local mobilities comparable to those in Ti₃C₂Tₓ. These mobilities represent intrinsic upper limits that could be realized in Ti₂CTₓ at macroscopic scales with improved oxidative stability and processing. Photoexcitation at both 400 nm and 800 nm induces a transient enhancement in THz conductivity, in contrast to Ti₃C₂Tₓ, where photothermal heating suppresses mobility. Most photoexcited carriers in Ti₂CTₓ recombine or become trapped within a few picoseconds, while a small fraction persists for hundreds of picoseconds. Photoinduced carriers exhibit longer scattering times and reduced localization compared to intrinsic carriers, suggesting that their excess kinetic energy allows them to overcome barriers from defects and oxidation. Excitation wavelength influences early-time dynamics: 800 nm excitation results in a slower rise and decay than 400 nm, consistent with inter-valley scattering between conduction-band valleys of differing mobility, or with initial excitation into low-mobility, defect-associated states followed by thermally activated de-trapping. These observations provide new insights into the complex pathways of photoexcitation and carrier evolution in Ti₂CTₓ.
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Details
- Title
- Terahertz Spectroscopy of Intrinsic and Photoexcited Carrier Dynamics in Ti₂CTx MXene Films
- Creators
- Kateryna Kushnir - Worcester Polytechnic InstituteStefano Ippolito - Drexel UniversityLaura L Fandiño - Worcester Polytechnic InstituteAndrew Michael Fitzgerald - Worcester Polytechnic InstituteYury Gogotsi - Drexel UniversityLyubov Titova (Corresponding Author) - Worcester Polytechnic Institute
- Publication Details
- 2d materials, v 13(3), Forthcoming
- Publisher
- Institute of Physics (IOP)
- Number of pages
- 10
- Grant note
- NSF: NRT-HDR-2021871 Gapontsev Family Collaborative Venture Fund Clare Boothe Luce Fellowship Army Research Laboratory: W911NF-19-2-0119, W911NF-24-2-0100
K.K.F. and L.V.T. acknowledge support from the Gapontsev Family Collaborative Venture Fund. S.I. and Y.G. acknowledge the Army Research Laboratory for supporting this work under Cooperative Agreements No. W911NF-19-2-0119 and W911NF-24-2-0100. AMF and LLF acknowledge support from the NSF under the NRT-HDR-2021871 fellowship grant. LLF also thanks The Clare Boothe Luce Fellowship.
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Materials Science and Engineering; A.J. Drexel Nanomaterials Institute
- Web of Science ID
- WOS:001827864400001
- Other Identifier
- 991022196565604721