Physical Origin of Negative Differential Resistance in V 3 O 5 and Its Application as a Solid-state Oscillator.

Oxides that exhibit an insulator-metal transition can be used to fabricate energy-efficient relaxation oscillators for use in hardware-based neural networks but there are very few oxides with transition temperatures above room temperature. Here we report the structural, electrical and thermal properties of V 3 O 5 thin films and their application as the functional oxide in metal-oxide-metal relaxation oscillators. The V 3 O 5 devices show electroforming-free volatile threshold switching and negative differential resistance (NDR) with stable (<3% variation) cycle-to-cycle operation. The physical mechanisms underpinning these characteristics are investigated using a combination of electrical measurements, in-situ thermal imaging and device modelling. This shows that conduction is confined to a narrow filamentary path due to self-confinement of the current distribution, and that the NDR response is initiated at temperatures well below the IMT temperature where it is dominated by the temperature dependent conductivity of the insulating phase. Finally, we report the dynamics of individual and coupled V 3 O 5 -based relaxation oscillators, and show that capacitively coupled devices exhibit rich non-linear dynamics, including frequency and phase synchronisation. These results establish V 3 O 5 as a new functional material for volatile threshold switching and advance the development of robust solid-state neurons for neuromorphic computing. This article is protected by copyright. All rights reserved.