Dynamic strain coupling driven by structural phase transition in mixed-dimensional 2H-MoS2/VO2 van der Waals heterointerfaces.

Mixed-dimensional van der Waals (vdW) heterostructures, integrated two-dimensional (2D) atomic crystals with three-dimensional (3D) functional materials, offer a powerful means to manipulating physical properties and generating unprecedented functionalities. Understanding interfacial couplings at those hetero (homo)-interfaces is indispensable for exploring new optical and electronic devices. Herein, we investigated dynamically phase-transition-driven strain coupling across a vdW heterointerface through integrating 2D layered 2H-MoS₂ nanoflakes onto 3D phase-change VO₂ epitaxial thin films. The Raman peak positions of the in-plane and out-of-plane vibration modes E 2 g 1 and A_1g from the 2H-MoS₂ nanoflakes show a phonon softening and reversible hysteresis loop as a function of temperature in this mixed-dimensional vdW 2H-MoS₂/( 1 ¯ 11)-VO₂/(1 1 ¯ 02)-Al₂O₃ heterostructure, originating from the co-action of temperature-dependent anharmonicity in 2H-MoS₂ and reversible structural phase transition (SPT)-induced in-plane tensile strain from the VO₂ thin film. Accordingly, the integrated Raman scattering intensity of these two feature peaks of the 2H-MoS₂ nanoflakes increased (decreased) as the temperature increased (decreased), exhibiting a hysteresis loop in the SPT and metal–insulator transition region of VO₂. Additionally, the peak integrated intensity enhancement ratio of the E 2 g 1 and A_1g vibration modes was approximately 2.3 and 2.8, respectively. These results indicate that the dynamically SPT-driven in-plane tensile strain from the bottom VO₂ layer interfacially couples with the adjacent 2H-MoS₂ nanoflakes and results in a reduction in the electronic transition energy, leading to an enhancement in the Raman scattering intensity of 2H-MoS₂. Our work holds promise for dynamic strain control of lattice dynamics and electron–phonon interaction of 2D materials for functional electronic and photoelectronic devices. [ABSTRACT FROM AUTHOR]