Time-Resolved Tracking of Hot Carrier Relaxation in Two Types of MBenes

Abstract

In metallic low-dimensional materials, the interaction between non-equilibrium electrons and phonons underlies various physical phenomena, such as the relaxation process of hot carriers. However, it is unclear how the surface, with or without termination, controls electron-phonon (e-p) interactions in two-dimensional (2D) transition metal borides (MBenes). Herein, ultrafast time-resolved spectroscopy was employed to measure the e-p interaction rate, revealing that MoB MBene without termination exhibits a lower rate than Mo_4/3B_2−xT_z MBene with termination, indicating that its e–p interactions are weakened. Raman spectra and computational calculations indicate that the suppression is attributed to the fact that the excited electrons can only couple with a limited number of vibrational modes. This study paves the way for the tailored manipulation of hot carrier relaxation time, offering opportunities for advanced applications in electronics, optoelectronics, catalysis, and more.