Freestanding Ordered Intermetallic Nanomembranes Released from Etchable Oxide Templates

Intermetallic compounds exhibit long-range atomic ordering that endows them with physicochemical properties distinct from those of elemental metals and disordered alloys. Extending ordered intermetallics into ultrathin, freestanding geometries is of both fundamental and technological interest, yet it remains challenging because the high temperatures required for chemical ordering exceed the thermal stability of conventional sacrificial templates. Here, we introduce water-etchable aluminate oxides as lattice-matched, thermally robust sacrificial templates for the epitaxial growth and nondestructive release of intermetallic nanomembranes. Using Pt₃Sn as a model system, we realize millimeter-scale freestanding membranes that preserve long-range chemical order and crystallographic orientation after being released. These nanomembranes maintain structural integrity and mechanical robustness during transfer and under mechanical loading, demonstrating their compatibility with flexible device architectures. Low-temperature magnetotransport measurements further reveal the preservation of quantum interference and multiband transport behaviors. This oxide template strategy establishes a generalizable synthetic pathway toward freestanding intermetallic nanomembranes and other ultrathin metal systems.