Controlling Conductive Filament and Tributyrin Sensing Using an Optimized Porous Iridium Interfacial Layer in Cu/Ir/TiN_xO_y/TiN

Controlling the copper (Cu) filament using an optimized porous iridium (Ir) interfacial layer thickness ranging from 2 to 20 nm in a Cu/Ir/TiN_xO_y/TiN resistive switching memory device is investigated for the first time. Transmission electron microscopy (TEM) shows a porous Ir layer, and X-ray photoelectron spectroscopy (XPS) is performed to determine the Ir⁰, Ir³⁺/Ir⁴⁺ oxidation states, which are responsible for a super-Nernstian pH sensitivity of 125.5 mV pH⁻¹ as well as a low concentration of 1 × 10⁻¹²m tributyrin detected using a 40 nm thick Ir in Ir/TiN_xO_y/TiN structure. The 5 nm thick Ir layer in the Cu/Ir/TiN_xO_y/TiN structure shows current–voltage switching characteristics for 3000 consecutive cycles, a stable RESET voltage, a long program/erase (P/E) endurance of >10⁹ cycles under a P/E current of 300 µA at a high speed of 100 ns, and neuromorphic phenomena compared to those of other Ir thicknesses. Cu migration into the TiN_xO_y oxide-electrolyte is shown by TEM observations. The tributyrin detection ranging from 1 × 10⁻¹² to 100 × 10⁻¹²m using a resistive switching memory device paves the way for the early diagnosis of human diseases as well as artificial intelligence applications in the near future.