Phase/Interfacial-Engineered Two-Dimensional-Layered WSe2 Films by a Plasma-Assisted Selenization Process: Modulation of Oxygen Vacancies in Resistive Random-Access Memory

Here, we propose phase and interfacial engineering byinsertinga functional WO3 layer and selenized it to achieve a 2D-layeredWSe(2)/WO3 heterolayer structure by a plasma-assistedselenization process. The 2D-layered WSe2/WO3 heterolayer was coupled with an Al2O3 filmas a resistive switching (RS) layer to form a hybrid structure, withwhich Pt and W films were used as the top and bottom electrodes, respectively.The device with good uniformity in SET/RESET voltage and high low-/high-resistancewindow can be obtained by controlling a conversion ratio from a WO3 film to a 2D-layered WSe2 thin film. The Pt/Al2O3/(2D-layered WSe2/WO3)/Wstructure shows remarkable improvement to the pristine Pt/Al2O3/W and Pt/Al2O3/2D-layered WO3/W in terms of low SET/RESET voltage variability (-20/20)%,multilevel characteristics (uniform LRS/HRS distribution), high on/offratio (10(4)-10(5)), and retention (& SIM;10(5) s). The thickness of the obtained WSe2 was tunedat different gas ratios to optimize different 2D-layered WSe2/WO3 (%) ratios, showing a distinctive trend of reducedand uniform SET/RESET voltage variability as 2D-layered WSe2/WO3 (%) changes from 90/10 (%) to 45/55 (%), respectively.The electrical measurements confirm the superior ability of the metallic1T phase of the 2D-layered WSe2 over the semiconducting2H phase. Through systemic studies of RS behaviors on the effect of1T/2H phases and 2D-layered WSe2/WO3 ratios,the low-temperature plasma-assisted selenization offers compatibilitywith the temperature-limited 3D integration process and also providesmuch better thickness control over a large area.