Bi ₂ O ₂ Se-Based Monolithic Floating-Gate Nonvolatile Memory with Enhanced Charge Retention and Switching Performance

High Resolution Image Download MS PowerPoint Slide The continuous scaling of conventional floating-gate memories faces major challenges due to charge leakage and complex multilayer architectures. Here, we report a monolithic nonvolatile memory (NVM) device constructed using a single 2D material, Bi 2 O 2 Se, that integrates channel, charge storage, and tunneling functions within the same material system. Upon UV–ozone treatment, semiconducting Bi 2 O 2 Se (s-BOS) forms a conformal and crystalline β-Bi 2 SeO 5 shell. Subsequent thermal annealing introduces selenium vacancies into the core, converting it to metallic Bi 2 O 2 Se (m-BOS), which serves as a floating-gate capable of efficient charge trapping, while the crystalline BOS oxide shell provides robust tunneling insulation and suppresses leakage. This monolithic structure integrates channel (s-BOS), storage (m-BOS), and tunneling functions (BOS oxide) within a single material system. The devices exhibit a large memory window, a high charge storage density (∼5 × 10 13 cm –2 ), and a current ON/OFF ratio exceeding 10 8 . They also show fast programming/erasing with ±12 V, 100 ms pulses, robust endurance over 2000 cycles, and charge retention exceeding 10 4 seconds. Compared with other 2D NVMs employing separate materials for each functional layer, this single-material platform enables simplified fabrication and improved scalability in the 2D memory device design.