Fig. 4: Terahertz conductivity spectra and inferred scattering time for semiconducting and metallic MXenes.
a, Complex photoconductivity for the semiconductor-like Nb4C3Tx thin film, measured at ~200 ps after photoexcitation at varying temperatures. b, Scattering times τ of Nb4C3Tx as a function of temperature. c, T-dependent scattering rate of Nb4C3Tx. d, Complex static terahertz conductivity (σopt) for metallic Ti3C2Tx thin films at varying temperatures. e, T-dependent scattering time of Ti3C2Tx. Inset: \({\omega _{\rm{p}}^2}\) at various T. The dashed lines serve as a guide to the eye. f, T-dependent scattering rate of Ti3C2Tx. In a and d, the real and imaginary parts of conductivity are shown in red and blue, respectively, and the solid lines represent the fits to the DS model explained in the main text. In c and f, the solid lines are results of a transport model that includes the acoustic phonon (black dashed line), the LO phonon (blue dashed line) and impurity scattering (orange dashed line), as described in the main text. The error bars in b, c, e and f are the standard deviations calculated from the fits. Triangles represent the carrier–acoustic phonon scattering rates obtained from the DFT calculations described in the text.
