Wafer-Scale\nFreestanding Monocrystalline Chalcogenide\nMembranes by Strain-Assisted Epitaxy and Spalling

Monocrystalline chalcogenide thin films in freestanding\nforms are\nvery much needed in advanced electronics such as flexible phase change\nmemories (PCMs). However, they are difficult to manufacture in a scalable\nmanner due to their growth and delamination challenges. Herein, we\nreport a viable strategy for a wafer-scale epitaxial growth of monocrystalline\ngermanium telluride (GeTe) membranes and their deterministic integrations\nonto flexible substrates. GeTe films are epitaxially grown on Ge wafers\nvia a tellurization reaction accompanying a formation of confined\ndislocations along GeTe/Ge interfaces. The as-grown films are subsequently\ndelaminated off the wafers, preserving their wafer-scale structural\nintegrity, enabled by a strain-engineered spalling method that leverages\nthe stress-concentrated dislocations. The versatility of this wafer\nepitaxy and delamination approach is further expanded to manufacture\nother chalcogenide membranes, such as germanium selenide (GeSe). These\nmaterials exhibit phase change-driven electrical switching characteristics\neven in freestanding forms, opening up unprecedented opportunities\nfor flexible PCM technologies.