Piezo strain–controlled phase transition in single-crystalline Mott switches for threshold-manipulated leaky integrate-and-fire neurons

Abstract

Electrical manipulation of the metal-insulator transition (MIT) in quantum materials has attracted considerable attention toward the development of ultracompact neuromorphic devices because of their stimuli-triggered transformations. VO₂ is expected to undergo abrupt electronic phase transition by piezo strain near room temperature; however, the unrestricted integration of defect-free VO₂ films on piezoelectric substrates is required to fully exploit this emerging phenomenon in oxide heterostructures. Here, we demonstrate the integration of single-crystalline VO₂ films on highly lattice-mismatched PMN-PT piezoelectric substrates using a single-crystal TiO₂-nanomembrane (NM) template. Using our strategy on heterogeneous integration, single-crystal-like steep transition was observed in the defect-free VO₂ films on TiO₂-NM-PMN-PT. Unprecedented <i>T</i>_MI modulation (5.2 kelvin) and isothermal resistance of VO₂ [Δ<i>R</i>/<i>R</i> (<i>E</i>_g) ≈ 18,000% at 315 kelvin] were achieved by the efficient strain transfer-induced MIT, which cannot be achieved using directly grown VO₂/PMN-PT substrates. Our results provide a fundamental strategy to realize a single-crystalline artificial heterojunction for promoting the application of artificial neurons using emergent materials.