Tuning resistive switching properties of WO<sub>3−</sub> <i> <sub>x</sub> </i>-memristors by oxygen vacancy engineering for neuromorphic and memory storage applications
Krishna Rudrapal, Maitreyo Biswas, Biswajit Jana, V Adyam, Ayan Roy Chaudhuri
Abstract
Abstract High density memory storage capacity, in-memory computation and neuromorphic computing utilizing memristors are expected to solve the limitation of von-Neumann computing architecture. Controlling oxygen vacancy ( V O ) defects in metal oxide thin film based memristors holds the potential of designing resistive switching (RS) properties for memory storage and neuromorphic applications. Herein, we report on RS characteristics of complementary metal–oxide–semiconductor compatible WO 3− x based memristors modulated by precisely controlled oxygen non-stoichiometry. Switchability of the resistance states has been found to depend strongly on the V O s concentration in the WO 3− x layer. Depending on x , the memristors exhibited forming-free bipolar, forming-required bipolar, and non-formable characteristics. Devices with moderate V O s concentration (∼5.8 × 10 20 cm −3 ) exhibited a large R off / R on ratio of ∼6500, and reset voltage-controlled multi-level resistance states. A forming-free, stable multi-level RS has been realized for a memristor possessing V O s concentration of ∼6.2 × 10 20 cm −3 . WO 3− x -based memristors with higher V O s concentrations (∼8.9 × 10 20 cm −3 –1 × 10 21 cm −3 ) exhibited lower initial resistance, low R off / R on ratios (∼15–63) and forming-free synaptic functions with reasonable conduction modulation linearity. Investigation of the conduction mechanism suggests that tailoring V O s concentration modifies the formation and dimension of the conducting filaments and the Schottky barrier height at the WO 3− x /Pt interface, which paves the way for designing WO 3− x -based memristors for memory storage and neuromorphic applications.