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

Surfaces and insulator-metal transition (IMT) are essential but challenging in IMT-triggered electronic switches and optical modulators. Reversible IMT suppression in vanadium dioxide electronic switching are achieved and controlled by reversible entropy-driven defect migration. Such reversible modulations will help understand the surface-driven phase change and IMT behaviors in correlated vanadium oxides towards advanced IMT-triggered devices.

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 (VO₂) 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 VO₂ 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 VO₂ nanobeam with M2 phase is accompanied by large variations in the IMT temperature. We also achieved irreversible and stable IMT by exploiting an Al₂O₃ 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.

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