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

Abstract

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 TiOx formation process for memristive devices with Cu/TiOx/Ti/Cu and Pt/TiOx/Ti/Pt layers. In the proposed device, active material TiOx 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 TiOx films. The conductivity improves with the insertion of more oxygen deficiency to TiOx. 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 TiOx 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 TiOx 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.