Low voltage nanophotonic resistive switch based on multi-tapered and engineered Cu-TiO2 structure on silicon with sensing capability

Abstract

A resistive switch with optically readable and electrically writable capabilities is proposed in an engineered configuration consisting of multi-tapered and ring structures of Cu-TiO2 on silicon. The device leverages the multifunctional properties of TiO2 to enable low-voltage operation, a high extinction ratio (ER), and enhanced endurance with sensing capability. Incorporating multiple tapered regions with rings in a hybrid plasmonic waveguide enables areas with varying densities of conduction filaments in the light propagation direction. The tapered sections enhance, while the rings mitigate, light-filament interaction. The desired device functionalities are achieved with a combination of tapering and rings by modulating the interaction between a light-metal/oxygen vacancy filament. Well-defined hysteresis curves at 1550 nm prove optical readout of electrically written states in 10 nm thin TiO2. An optical ER of 20 dB is reported for a 10 μm long device. Furthermore, it demonstrates an intrinsic stochastic property that lowers the set voltage in each set-reset sweep. In addition, the UV application on the device further lowers the set voltage. The lowered set voltage across multiple cycles preserves hysteresis and ensures high endurance. Additionally, the proposed device demonstrates CO2 sensing based on the resistive switching phenomenon. Sensing capability, a high ER, and low voltage operation of the presented device pave the way for ultra-compact on-chip devices for optical switching and neuromorphic computing. © 2026 Elsevier B.V.