| Abstract Scope |
This talk examines how the Ta crystalline phase influences synaptic switching in ultrathin TaOx memristors formed by ultraviolet-ozone (UVO) treatment of sputter-deposited Ta films. The Ta phase is tuned between cubic and tetragonal by adjusting the deposition base pressure, with lower pressure (∼10-7 Torr) favoring the cubic phase. ~3 nm TaOx derived from cubic Ta shows reduced switching variability and improved endurance (up to 106 cycles) compared to that from tetragonal Ta. In contrast, in TaOx/HfOx bilayer devices, TaOx derived from tetragonal Ta enables forming-free switching, whereas cubic-derived TaOx does not. These behaviors are attributed to differences in the spatial distribution of oxygen vacancies, supported by synchrotron variable-energy X-ray photoemission spectroscopy (VE-XPS) and high-resolution transmission electron microscopy. |