Atomic-Level Structure Determines Electron–Phonon Scattering Rates in 2-D Polar Metal Heterostructures

The performance of nanoscale metals in applications such as plasmonics, photodynamic therapy, andphotocatalysis is influenced by their ability to absorb and transduce energy to their surroundings. In this study, we measured the nonequilibrium carrier dynamics in an air-stable 2-D polar metal heterostructures. Using transient absorption spectroscopy, the mechanism for energy dissipation was determined to involve contributions from the various components of the heterostructure, including the 2-D metal layer, SiC substrate, and graphene capping layer. The rate of relaxation for these heterostructures is influenced by alloying, with a Ga/In alloy exhibiting an approximately 3-fold increase in electron-phonon coupling rate compared to Ga or In alone. Correlative nonlinear optical microscopy and electron microscopy revealed the presence of atomic-level disorder in alloyed 2-D metals, which influences the energy dissipation rates and excitation of in-plane shear phonon modes. This observation points towards the potential to tune energy transduction through modifications to the metal lattice, which can be monitored through far-field nonlinear optical microscopy. This study was published in ACS Nano 15, 11, 17780 (2021).