Resistive Switching Behaviour and Spiking Time Dependent Plasticity of PLD Grown VO₂/TiO₂ Thin Films Supplemented by Discrete Wavelength of Light

Electronic computing is undergoing a paradigm shift with the advent of neuromorphic architecture from the archetype von Neuman architecture. In neuromorphic architecture [1], data processing occurs within the storage memory, eradicating the data latency period. The overall data processing speed reduces acutely, further decreasing energy costs. A memristor is a highly scalable fundamental circuit component that switches across multiple stable states [2] at a very low energy cost, deeming it suitable for neuromorphic application. Transition metal oxides (TMOs) are suitable materials for the fabrication of these memristive components [3] showcasing resistive switching due to physiochemical mechanisms based on ion migration, electrolyte gated, phase change, ferroelectric, spintronic, photonic migration, electronic migration, and metal-insulator transition. Owing to the abundance of materials showing MIT for vested interest of neuromorphic application VO₂ shows MIT at near room temperature [4]. VO₂ undergoes a transition from the low-temperature monoclinic (M1) phase to the tetragonal (R) phase at a temperature above 68 ^○C, along with the occurrence of several unstable phases during the transition. The transition temperature of VO₂ can also be tuned to a higher or lower value under the effect of tensile or compressive strain in the lattice under the influence of an electric field, magnetic field, and the illumination of a specific wavelength of light [5]. VO₂/TiO₂ memristor fabricated using pulsed laser deposition, when illuminated with a laser source of 405 nm, 532 nm, 633 nm, and 980 nm, shows changes in memristive properties like R_OFF/R_ON ratio and switching power. In order to concretize the functioning of the memristor as an artificial synapse, spiking time-dependent plasticity (STDP) analysis [6] is performed under different illumination conditions to boot.

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