Periodic Wrinkles in Freestanding Complex Oxide Membranes

A stiff film bonded to an elastic substrate shows a universal tendency to form periodic wrinkles upon application of compressive force [1]. This design principle has been employed to produce wafer-scale wrinkles in polycrystalline metal films on polydimethylsiloxane (PDMS) for applications in <i>e.g.</i> optical gratings or strain sensors [2]. When a single crystalline film is processed similarly in a non-planar morphology, a spatially gradated strain state with continuously varying lattice constant can be realized. In the regime of extreme bending, the strain gradient therein is known to generate significant modifications in mechanical and electromagnetic properties of the material [3,4]. The recent development of water-soluble oxide buffer layer enables viable lift-off of complex oxide membranes to be transferred onto an arbitrary elastic substrate [5]. In this study, we adopt this technique to prepare single crystalline oxide membranes on PDMS and fabricate a variety of periodic wrinkles in a fully programmable fashion using compression amplitude and membrane thickness as control parameters. Under large compressive force, the degree of bending extends to the limit where the membrane thickness is a few percent in size compared to the radius of curvature of wrinkles. In addition, we introduce our unique sample packaging methods to characterize electrical properties of wrinkled membranes while maximally preserving the overall sample geometry and the associated strain state.<br/><br/>References:<br/>[1] Z. Y. Huang <i>et al</i>., J. Mech. Phys. Solids 53, 2101 (2005)<br/>[2] T. Ma <i>et al</i>., Opt. Express 21, 11994 (2013)<br/>[3] G. Dong <i>et al</i>., Science 366, 475 (2019)<br/>[4] V. Harbola <i>et al</i>., Nano Lett. 21, 2470 (2021)<br/>[5] D. Lu <i>et al</i>., Nat. Mater. 15, 1255 (2016)