Controlling Resistive Switching by Using an Optimized MoS ₂ Interfacial Layer and the Role of Top Electrodes on Ascorbic Acid Sensing in TaO _x -Based RRAM

Controlled resistive switching by using an optimized 2 nm thick MoS ₂ interfacial layer and the role of top electrodes (TEs) on ascorbic acid (AA) sensing in a TaO _x -based resistive random access memory (RRAM) platform have been investigated for the first time. Both the high-resolution transmission electron microscopy (HRTEM) image and depth profile from energy dispersive X-ray spectroscopy confirm the presence of each layer in IrO _x /Al ₂ O ₃ /TaO _x /MoS ₂ /TiN structure. The pristine device including the IrO _x TE with the 2 nm thick interfacial layer shows the highest uniform rectifying direct current endurance >1000 cycles and a large rectifying ratio >3.2 × 10 ⁴ , and a high nonlinearity factor >700 is obtained, greater than that of Pt and Ru TEs. After formation, this IrO _x device produces bipolar resistive switching characteristics and a long program/erase (P/E) endurance >10 ⁷ cycles at a low operation current of <50 μA with small pulse width of 100 ns. The stressed device shows a reduced Al ₂ O ₃ /TaO _x interface from the HRTEM image, which is owing to O ^2- ions' migration toward TiN electrode. By adjusting the RESET voltage and current level, consecutive >100 complementary resistive switching as well as long P/E endurance of >10 ⁶ cycles are obtained. Schottky barrier height modulation at a low field is observed owing to reduction-oxidation of the TE, which is evidenced through reversible AA detection. At a higher field, Fowler-Nordheim tunneling and hopping conduction are observed. Ascorbic acid detection with a low concentration of 1 pM by using a porous IrO _x /Al ₂ O ₃ /TaO _x /MoS ₂ /TiN RRAM device directly is an additional novelty of this work, which will be useful in future for early diagnosis of scurvy.