# Emergent Freestanding Complex Oxide Membranes for Multifunctional Applications

## TL;DR

This review explores freestanding oxide membranes and their potential for creating multifunctional devices by examining different fabrication methods and challenges.

## Contribution

The paper provides a comprehensive review of freestanding oxide membranes, focusing on their properties and pathways for device development.

## Key findings

- Freestanding oxide membranes offer tunable properties for multifunctional devices.
- Three development pathways—strain-free, strained membranes, and van der Waals heterostructures—are highlighted.
- Challenges include achieving high-quality surfaces and wafer-scale manufacturing.

## Abstract

Correlated complex oxides feature tightly coupled charge, spin, orbital, and lattice degrees of freedom, which give rise to rich correlated behavior. Freestanding oxide membranes render these materials into tunable quasi‐2D platforms that enable multifunctional and reconfigurable devices. This Review surveys recent advances in the research of freestanding oxide membranes, highlighting their coupled correlated properties. We focus on three development pathways: (i) strain‐free membranes, (ii) strained membranes, and (iii) van der Waals‐integrated heterostructures. This organization begins with the intrinsic properties of oxide membranes, then examines mechanical tuning, heterogeneous integration, and multiphysics coupling to provide a comprehensive account of the field's development. Finally, we evaluate practical challenges, including high‐quality surfaces, robust multiphysics coupling, wafer‐scale transfer, and silicon‐compatible heterogeneous integration. Addressing these challenges will enable scalable, high‐yield manufacturing and expand the design space for oxide‐based architectures, thereby accelerating the transition from laboratory demonstrations to industry‐ready systems.

This review surveys freestanding oxide membranes and covers fabrication and three pathways for studies and devices: strain‐free and strained membranes, and van der Waals‐integrated heterostructures. We show how coupled oxide responses map onto these routes and cross‐couple to expand behaviors. We identify barriers to scalable multifunctional devices and outline considerations for membrane quality, heterostructure construction, Si‐compatible processing, and wafer‐scale handling.