Highly Reliable MoS2 Flash Memory with Ultrathin TaOx Tunneling Layer Formed via Partial Oxidation of TaS2 Floating Gate.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) are regarded as promising candidates for next-generation semiconductor devices due to their atomically thin structure enabling highly efficient short channel effect-free electrostatic control. In particular, low power consumption and high reliability induced by ultrathin heterostructures with clean van der Waal interfaces make 2D TMDs highly attractive for flash memory applications. Among the TMDs, tantalum disulfide (TaS2) behaves as a metal with a work function of ∼5.6 eV and readily undergoes oxidation. In this study, we propose a 2D MoS2 flash memory device incorporating the oxidation property of TaS2, which is used for charge trapping. We found that a thickness-controlled high-quality tantalum oxide (TaOx) layer is formed on the surface of TaS2 through time- and temperature-adjusted ultraviolet ozone (UVO) treatments, serving as a tunneling insulator in a charge trapping stack. This approach produces a precisely controlled TaOx tunneling layer, achieving a large hysteresis-to-gate sweep range ratio of 74.3% and a reliable retention with an on/off current ratio exceeding 103 after 10,000 s in a flash memory device with MoS2 channel. Effects of oxide thickness, controlled by temperature during UVO treatment, on charge trapping properties and hysteresis behavior were systematically investigated to obtain the best memory characteristics. Furthermore, the TaOx/TaS2 charge trapping stack is demonstrated to be universally applicable to the other 2D TMD WSe2. These results suggest that the proposed UVO-based self-formation of charge trapping and tunneling layers in 2D metals represents a promising strategy for achieving high reliability and performance in flash memory devices, contributing significantly to advancements in 2D material-based memory technologies.