Control of Charge Carrier Relaxation at the Au/WSe<sub>2</sub> Interface by Ti and TiO<sub>2</sub> Adhesion Layers: Ab Initio Quantum Dynamics
Teng-Fei Lu, Sraddha Agrawal, Marina V. Tokina, Weibin Chu, Daniel Hirt, Patrick E. Hopkins, Oleg V. Prezhdo
Abstract
Phonon-mediated charge relaxation plays a vital role in controlling thermal transport across an interface for efficient functioning of two-dimensional (2D) nanostructured devices. Using a combination of nonadiabatic molecular dynamics with real-time time-dependent density functional theory, we demonstrate a strong influence of adhesion layers at the Au/WSe2 interface on nonequilibrium charge relaxation, rationalizing recent ultrafast time-resolved experiments. Ti oxide layers (TiOx) create a barrier to the interaction between Au and WSe2 and extend hot carrier lifetimes, creating benefits for photovoltaic and photocatalytic applications. In contrast, a metallic Ti layer accelerates the energy flow, as needed for efficient heat dissipation in electronic devices. The interaction of metallic Ti with WSe2 causes W–Se bond scissoring and pins the Fermi level. The Ti adhesion layer enhances the electron–phonon coupling due to an increased density of states and the light mass of the Ti atom. The conclusions are robust to presence of typical point defects. The atomic-scale ab initio analysis of carrier relaxation at the interfaces advances our knowledge in fabricating nanodevices with optimized electronic and thermal properties.