Freestanding Membranes*

LaAlO₃/SrTiO₃ heterointerfaces have been used to create reconfigurable nanoelectronic devices based on nanoscale control of LAO/STO metal-to-insulator transition. The realization of freestanding membrane based on LAO/STO heterostructures and the capability of creating reversible patterns of nanoscale conducting regions open opportunities to integrate heterostructures with Si-based architectures [1]. In particular, the integration of flipped STO/LAO membranes on Si will enable us to create reconfigurable Si-based nanodevices for storage and gating of electrons and spins. We have fabricated flipped freestanding membranes of LAO/STO heterostructures and transferred them onto Si. First, we deposited epitaxial LAO/STO heterostructures on (001) STO substrates with a Sr₂Ca₁Al₂O₆ sacrificial layer by pulsed laser deposition. Subsequent selective etching yielded freestanding membranes, which were collected by a wire loop. By flipping the wire loop over, flipped STO/LAO membranes were then integrated with Si via van der Waals stacking. The flipped membranes, with dimensions on the millimeter scale, preserved atomically smooth surface with step-terrace structure and high crystallinity. ULV-EBL technique has demonstrated the capability of switching flipped STO/LAO heterointerfaces to conducting state from insulating. In this talk, I will discuss the integration of flipped STO/LAO membranes with Si, which will allow the fabrication of Si-based field-effect transistor devices utilizing STO/LAO 2DEG as metallic gates. We anticipate that the advantage of flipped STO/LAO heterostructures will enable the high-resolution gate patterning of quantum devices, and further provide a new quantum material host system for storing and processing quantum information.

[1] Eom, K., et al. Science advances 7, 33 (2021)