The effect of changing electrode metal on solution-processed flexible titanium dioxide memristors

Abstract Flexible solution-processed memristors show different behaviour dependent on the choice of electrode material. Use of gold for both electrodes leads to switchable WORM (Write Once Read Many times) resistive devices. Use of aluminium for both electrodes allows both curved (wholly non-linear) and triangular (linear ohmic low resistance state) memristive switching resistance memories. A comparison device with an aluminium bottom electrode and gold top electrode only exhibited significant memristive resistance switching when the aluminium electrode was the anode, suggesting that the electrode is acting as a source/sink of oxygen anions. Using the gold electrode as the anode causes oxygen evolution and electrode deformation. We conclude aluminium is helpful for stabilising and promoting memristive behaviour in sol-gel TiO₂ devices. On and Off resistance states were found to correlate to device size, and the relative proportions of curved to triangular switching devices could be affected by vacuum curing of the gel layer and compliance current. We postulate that: A. the curved memristor switching is a bulk action compliant with Chua's description of a memristor; B. the triangular switching involves a filament conduction for the ohmic low resistance state.