Speaker
Description
Probing charge carrier dynamics across a broad frequency range — from terahertz (THz) to infrared (IR) regimes — presents a powerful, contact-free procedure to investigate nanoscale transport phenomena in low-dimensional materials. Combining frequency dependent optical conductivity spectra with conventional d.c. electrical measurements enable a comprehensive picture of carrier transport mechanisms in morphologically complex systems such as solution processed 2D materials.
Here, we report a systematic investigation of charge transport in thin films of 2D Ti₃C₂Tₓ MXene over an exceptionally wide spectral range (d.c. + 0.3 - 80 THz). Films of varying thickness were fabricated by convection-assisted self-assembly at the liquid–air interface, yielding well-controlled 2D flake networks on semi-insulating Si substrates. Non-zero d.c. conductivity across all samples confirms a percolated network, validated by microstructure analysis via. optical and electron microscopy. Systematic increase of the real conductivity in the frequency range ~ 0.2 - 16 THz reveals partial carrier localization. Broadband fitting using the modified Drude-Smith model demonstrates a clear correlation between the localization rate and the characteristic MXene flake size. At higher frequencies, a crossover to intrinsic Drude behavior — marked by decreasing conductivity and increasing optical transparency — is observed. We further discuss the systematic evolution of transport parameters as a function of film thickness, providing design guidelines for MXene-based optoelectronic and electromagnetic applications.