Freestanding oxide membranes:synthesis,tunable physical properties,and functional devices

The study of oxide heteroepitaxy has been hindered by the issues of misfit strain and substrate clamping,which impede both the optimization of performance and the acquisition of a fundamental understanding of oxide systems.Recently,however,the development of freestanding oxide membranes has provided a plausible solution to these substrate limitations.Single-crystalline functional oxide films can be released from their substrates without incurring significant damage and can subsequently be transferred to any substrate of choice.This paper discusses recent advancements in the fabrication,adjustable physical properties,and various applications of freestanding oxide perovskite films.First,we present the primary strategies employed for the synthesis and transfer of these freestanding perovskite thin films.Second,we explore the main functionalities observed in freestanding perovskite oxide thin films,with special attention to the tunable functionalities and physical properties of these freestanding perovskite membranes under varying strain states.Next,we encapsulate three representative devices based on freestanding oxide films.Overall,this review highlights the potential of freestanding oxide films for the study of novel functionalities and flexible electronics.

Lateral strain tailoring in manganite homostructures assisted by atomic-flat freestanding membranes

Complex oxide thin films exhibit intriguing phenomena due to the coupling between multiple degrees of freedom through interfacial structural engineering.Atomic tailoring of structural parameters determines unique band structure and phonon modes,regulating emergent magnetic and electrical properties of oxide films.However,the construction of different strained and oriented domains in one intact oxide thin film is impossible using conventional means.Here we report the fabrication and quantitative structural analysis of La_(0.7)Sr_(0.3)MnO_(3)(LSMO)homostructures assisted by atomic-flat freestanding membranes.Pristine substrates and suspended membranes regulate the epitaxial strain and orientation of subsequently grown films.Our results demonstrate an ultrathin transition layer(~4 atomic layers)between freestanding membranes and LSMO films is formed due to the strain relaxation.This work offers a simple and scalable methodology for fabricating unprecedented innovative functional oxide homostructures through artificially controlled synthesis routes.

Enhanced ferromagnetism and conductivity of ultrathin freestanding La_(0.7)Sr_(0.3)MnO_(3)membranes

We report a universal method to transfer freestanding La_(0.7)Sr_(0.3)MnO_(3)membranes to target substrates.The 4-unit-cell-thick freestanding La_(0.7)Sr_(0.3)MnO_(3)membrane exhibits the enhanced ferromagnetism,conductivity and out-of-plane magnetic anisotropy,which otherwise shows nonmagnetic/antiferromagnetic and insulating behavior due to the intrinsic epitaxial strain.This work facilitates the promising applications of ultrathin freestanding correlated oxide membranes in electronics and spintronics.