Strain Engineering of Complex Oxide Membranes on Flexible Metallic Support

Abstract

Controlling material functionalities via external stimuli is a cornerstone of modern science and technology. One effective strategy involves tuning mechanical strain, which can be induced through lattice mismatch, electric fields, or applied mechanical force. Recent advances in fabricating freestanding single-crystalline complex oxide membranes have opened new opportunities for integrating these materials onto previously incompatible platforms such as metals and flexible polymers for next-generation device applications. A key step in strain engineering is understanding and controlling the integration of such materials with flexible substrates. In this study, the integration and adhesion of freestanding single-crystalline La_0.7Sr_0.3MnO₃ (LSMO(001)) membranes onto metallic surfaces (Au, Pt, and TiN) coated on flexible polymer substrates is demonstrated. It is found that the choice of metal underlayer significantly influences the ability to strain the membrane. Using TiN-coated polymer support, a uniform strain of ≈1% in LSMO membranes, along with strong adhesion between the membrane and substrate, is achieved. Theoretical calculations reveal that strong Ti─O bonding and compact in-plane lattice matching at the LSMO(001)/TiN(111) interface lower the interface formation energy compared to noble metals. These findings offer valuable insights for selecting suitable platforms to apply external mechanical stress to freestanding oxide membranes, facilitating their integration into flexible electronic systems.