Flexible Metal-Insulator Transitions Based on van der Waals Oxide Heterostructures.

Recently, flexible and wearable electronics are highly desirable because of their great potential in the next-generation information devices. In this work, we demonstrate the realization of the metal-insulator transition (MIT) effect in flexible rare-earth nickelate heterostructures. The NdNiO ₃ thin films are grown on lattice-mismatched mica substrates along the pseudocubic (111) direction via the van der Waals heteroepitaxy, in which the MIT behaviors are induced and modulated by carefully controlling the lattice strain and the ionic valence state with SrTiO ₃ and LaAlO ₃ buffering layers. Enhanced MIT properties with sharp transition and significant resistivity change between the metallic and the insulating states are achieved in the NdNiO ₃ /LaAlO ₃ /SrTiO ₃ /mica heterostructures with appropriate in-plane tensile strain and suppressed concentration of Ni ²⁺ ions. In addition, the proposed NdNiO ₃ -based heterostructures exhibit excellent flexibility with reliable MIT characteristics not only in statically concave/convex bending but also in dynamically bending cycling up to 1000 times. The present work provides a platform to design and fabricate new flexible devices integrated with the MIT effect.