Environmental Temperature's Impact on Ultrafast Photoacoustic Conversion in 2D Layered Semiconductor/3D Dielectric Heterostructure

Abstract For a 2D layered semiconductor/3D dielectric heterostructure, longitudinal coherent acoustic phonon (CAP) oscillation of 2D layers can emit a picosecond acoustic (PA) pulse into 3D materials. However, the environmental temperature's impact on the ultrafast photoacoustic conversion across the van der Waals heterointerface remains elusive. Here, employing femtosecond laser pump‐probe, the dynamical correlation between CAP oscillations and emitted PA pulses are experimentally investigated in a MoS ₂ /SiO ₂ heterostructure when varying the environmental temperature from 294 to 364 K. It turns out that interlayer expansion of MoS ₂ layers leads to a redshift of CAP oscillation frequency. Meanwhile, enhanced phonon scatterings both in MoS ₂ layers and at the MoS ₂ /SiO ₂ heterointerface collectively reduce ultrafast photoacoustic energy conversion efficiency. The results provide insights for understanding heat‐mediated ultrafast photoacoustic conversions in a 2D layered semiconductor heterostructure.