Size-Controlled Spalling of LaAlO₃/SrTiO₃ Micromembranes

Abstract

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Freestanding Perovskite Oxide Films: Synthesis, Challenges, and Properties

“…c) Top panel reproduced with permission. [ 16 ] Copyright 2021, American Chemical Society. Bottom two panels reproduced with permission.…”

“…As expected for the spalling process, the parallel fracture occurred below the tensile LAO and each membrane contains an LAO/STO interface. Dahm et al [ 16 ] showed that by pre‐patterning of the growth substrate using lithography and ion milling, the lateral locations of cracks can be controlled. This procedure enabled the controlled formation of free‐standing LAO/STO micro membranes with sizes from 2 to 20 µm.…”

“…Also, by mechanical micro‐manipulation individual membranes were transferred to silicon substrates and electrical devices were fabricated using lithography. [ 16 ]…”

“…This possibility has led to significant advances in the field, for example, with demonstration of freestanding LaAlO 3 /STO membranes on silicon substrates that contain a 2D electron gas exhibiting also superconductivity at low temperature. [15,16] Another important prospect of freestanding membranes is the emergence of different functionalities when compared with the substrateclamped counterpart. This section will cover representative seminal works where new functional properties not found in the substrate-supported thin film have arisen.…”

“…Different strategies for fabricating freestanding layers have been demonstrated as illustrated in Figure 1 : 1) Freestanding thin films using wet etching of sacrificial layers; [ 12,13 ] 2) Mechanical exfoliation method of epitaxial oxide crystals; [ 14 ] and 3) Self‐formed freestanding thin films through spalling. [ 15,16 ] Recently, heterostructures have also been fabricated by stacking membranes directly. [ 14 ] These results demonstrate an exciting general approach for producing freestanding thin films and multilayers.…”