Optical quantification of the weak van der Waals coupling between multilayer antimonene and bilayer MoS₂ using ultrafast coherent vibration spectroscopy

Antimonene, a promising conductor for next-generation 2D-based devices, has its contact resistance significantly influenced by the van der Waals (vdW) interaction within its heterostructure. In this study, we report the quantification of the vdW coupling between multilayer antimonene and bilayer MoS₂ by ultrafast coherent vibration spectroscopy. By utilizing a femtosecond laser, we excited coherent acoustic vibrations in the multilayer-antimonene on substrate-supported bilayer MoS₂, and the relative displacement at the vdW heterojunction was detected with the aid of bilayer MoS₂. The photoexcited strain pulse generated in the multilayer-antimonene was observed as it transported to the bilayer MoS₂, explaining the distortion at the beginning of the oscillation. By analyzing the thickness-dependent oscillation frequencies, we determine the effective vdW elastic constant between multilayer-antimonene and MoS₂ to be (1.9 ± 0.2) × 10¹⁸ N/m³. This non-destructive optical technique offers a significant advance in the evaluation of vdW interactions at 2D metal-semiconductor interfaces.