Flexoelectricity in ripple-engineered monolayer MoS2

Two-dimensional transition metal dichalcogenides (2D-TMDCs), particularly monolayer (1L) MoS2, are promising for next-generation flexible and piezoelectric devices due to their intrinsic piezoelectricity arising from broken inversion symmetry. However, achieving controlled 1L-growth and effective strain-engineering remains challenging, as conventional methods often produce multilayer islands and non-uniform strain distributions. Here, we use a scalable edge-enabled liquid–solid deposition (ELSD) method to reliably grow 1Ls-MoS2. In flakes, rapid cooling induces thermal expansion coefficient (TEC)-mismatch tensile strain, forming vein-like and threefold hierarchical ripples; continuous films exhibit coalescence-driven lattice mismatch, producing directional wrinkles. Multimodal characterization confirms 1L-thickness, well-defined local strain, and associated flexoelectric enhancement. These periodic strain patterns generate local strain in distinct regions (≈0.162% ± 0.008% in region-I and ≈0.203 ± 0.091% in region-II) that boost the intrinsic piezoelectric response via flexoelectricity, with region-II exhibiting a 40.2% higher electromechanical response than region-I, revealing a controllable flexoelectric mechanism in 2D-TMDCs. The findings open new pathways for nanoscale energy harvesting, nanogenerators, actuators, and flexible strain-programmable sensors.