Electric field induced Mott transition and bipolar resistive switching in La₂Ti₂O_7-x thin film

The oxygen ion migration-induced resistive switching is a complex process with multiple mechanisms. This study investigated resistive switching properties and mechanism for strongly correlated materials lanthanum titanium oxide La₂Ti₂O_7-x (LTO) using spectromicroscopy and density functional theory simulation. Bipolar resistive switching without an electroforming process was first reported in LTO film. The mechanism can be explained by oxygen ion migration induced band-filling controlled Mott transition in LTO. Oxygen ion migration-induced reduction and oxidation of LTO can increase and decrease Ti 3d orbital filling state, which in turn increases and reduces Mott-Hubbard gap and LTO resistance, respectively. In addition, the RRAM device, TiN/LTO/Pt, shows stable endurance, retention, and small variability at room temperature and 85 ℃, with a stable on/off-state current density, which is independent of the electrode size. This work not only demonstrates that LTO and other strongly correlated materials are potential candidates to prepare resistive random access memory based on oxygen ion migration induced Mott-transition mechanism but also indicates that intrinsic resistance change in switching layers between top and bottom electrodes also contribute to overall resistive switching.