Memristive behavior of TiO_x obtained via Pb(II)-assisted anodic oxidation process

Memristive devices are of promising systems enabling the potential applications of neuromorphic circuits, logical operations, and non-volatile memories. This study introduces a low-cost and feasible TiO_x formation process for memristive devices with Cu/TiO_x/Ti/Cu and Pt/TiO_x/Ti/Pt layers. In the proposed device, active material TiO_x is produced by anodic oxidation of Ti using cyclic voltammetry in 100 mM Methane sulfonic acid (CH₃SO₃H) aqueous solution containing Pb(CH₃SO₃)₂. The influence of Pb²⁺ content in the anodic oxidation process is evaluated using cyclic voltammetry and electrochemical impedance spectroscopy (EIS). Particularly, EIS results indicate that an increase in the Pb²⁺ content in the solution improves the conductivity of TiO_x films. The conductivity improves with the insertion of more oxygen deficiency to TiO_x. The structural identity and oxide thicknesses are worked out using Scanning Electron Microscopy, Low Angle X-Ray Diffraction (XRD) and Ellipsometry. Addition of Pb²⁺ to CH₃SO₃H solution significantly improves the oxidation rate and increasing the amount of Pb²⁺ in the solution produces a thicker oxide layer. Low Angle XRD analysis suggests the TiO_x formation, including oxygen-deficient (Magneli) phase, on Ti. Our findings indicate that during the anodic oxidation, a soluble oxygenated Pb⁴⁺ compound, (Pb(OH)₂²⁺), occurs and instead of contributing to PbO₂ deposition, it shows a catalytic effect on TiO_x formation. I–V measurements are conducted to investigate memristive behavior. Increasing the amount of Pb²⁺ content in the anodization solution yields wider hysteresis referring to more distinguishable ON/OFF states for electronic applications.