Thickness-dependent crack suppression and wrinkle formation in freestanding BaTiO3 membranes

Abstract

Freestanding ferroelectric oxide membranes offer a promising route toward silicon-integrated low-power electronic and memory devices, but reproducible membrane quality remains challenging, particularly in ultrathin BaTiO 3 (BTO), where cracking and wrinkling hinder integration. Here, we show that crack and wrinkle formation in released BaTiO 3 membranes can be tuned by jointly controlling oxide thickness and polymer support thickness. Reducing the BaTiO 3 thickness from 15 to 5 nm suppresses large-area, optically visible cracking across the analyzed regions, but promotes dense nanoscale wrinkling, revealing a trade-off between fracture mitigation and morphological instability. In 10-nm BaTiO 3 membranes, polymer support thickness further modulates wrinkling, with an intermediate thickness reducing wrinkle density. Piezoresponse force microscopy reveals time-dependent evolution of written contrast after release, indicating that apparent ferroelectric response is influenced by polarization switching, post-release morphology, interfacial contact, charge screening, and strain relaxation. These results establish processing guidelines for integrating freestanding ferroelectrics into future devices.