Defect-Induced Resistive Switching in Titanate-Based Perovskites

Memristive behavior characterized by switchable resistance states retaining memory has been recently observed in thin films of titanate-based perovskites grown under Ti-rich conditions, suggesting a defect-mediated origin [1]. To understand this, we investigate the defects behavior in ATiO₃ (A = Sr, Ca, Ba) using density functional theory with hybrid functional. Under the experimental growth conditions, the defect complex Ti antisite (Ti-interstitial with A-vacancy) is energetically favorable and acts as an electron donor. An additional A-site vacancy, which serves as an electron acceptor, further stabilizes the antisite defect and compensates its charge. The off-center shift of the interstitial atom induces a local polarization. This polarization is switchable between different off-center positions of the defect, with energy barriers between 0.1 and 0.8 eV depending on the migration pathway. Additionally, the Ti antisite defect gives rise to mid-gap states, with a charge density localized primarily around the Ti-interstitial atom. Switching defect between equivalent off-center positions switches the polarization direction and alters the spatial distribution of this charge density. This can influence the material’s overall response under external stimuli. These results are discussed with respect to the experimentally observed resistive switching in titanate-based perovskites.

[1] A. Baki et al., Sci. Rep. 11, 7497 (2021).