Reversible Entropy‐Driven Defect Migration and Insulator‐Metal Transition Suppression in VO₂ Nanostructures for Phase‐Change Electronic Switching

Abstract

Oxygen defects are among essential issues and required to be manipulated in correlated electronic oxides with insulator-metal transition (IMT). Besides, surface and interface control are necessary but challenging in field-induced electronic switching towards advanced IMT-triggered transistors and optical modulators. Herein, we demonstrated reversible entropy-driven oxygen defect migrations and reversible IMT suppression in vanadium dioxide (VO 2 ) phase-change electronic switching. The initial IMT was suppressed with oxygen defects, which is caused by the entropy change during reversed surface oxygen ionosorption on the VO 2 nanostructures. This IMT suppression is reversible and reverts when the adsorbed oxygen extracts electrons from the surface and heals defects again. The reversible IMT suppression observed in the VO 2 nanobeam with M2 phase is accompanied by large variations in the IMT temperature. We also achieved irreversible and stable IMT by exploiting an Al 2 O 3 partition layer prepared by atomic layer deposition (ALD) to disrupt the entropy-driven defect migration. We expected that such reversible modulations would be helpful for understanding the origin of surface-driven IMT in correlated vanadium oxides, and constructing functional phase-change electronic and optical devices.

Enabling Reconfigurable Resistive Switching via Tailored Multimodal Phase Transition

“…The controllable change in the ratio of M1 and M2 phases in VO 2 indicated diverse conductivity modes, i.e., mode n. Notably, VO 2 with the M2 phase owned much higher transition energy than VO 2 of M1 phase, and T phase exhibited variable V−V chains. 33 That is, the proportion changes of these phases directly affected the process of resistive switching, which helped to provide flexible control of switching thresholds.…”