Scalable cross-point resistive switching memory and mechanism through an understanding of H2O2/glucose sensing using an IrOx/Al2O3/W structure

The resistive switching characteristics of a scalable IrOx/Al2O3/W cross-point structure and its mechanism for pH/H2O2 sensing along with glucose detection have been investigated for the first time. Porous IrOx and Ir3+/Ir4+ oxidation states are observed via high-resolution transmission electron microscope, field-emission scanning electron spectroscopy, and X-ray photo-electron spectroscopy. The 20 nm-thick IrOx devices in sidewall contact show consecutive long dc cycles at a low current compliance (CC) of 10 mu A, multi-level operation with CC varying from 10 mu A to 100 mu A, and long program/erase endurance of 4109 cycles with 100 ns pulse width. IrOx with a thickness of 2 nm in the IrOx/Al2O3/SiO2/p-Si structure has shown super-Nernstian pH sensitivity of 115 mV per pH, and detection of H2O2 over the range of 1-100 nM is also achieved owing to the porous and reduction-oxidation (redox) characteristics of the IrOx membrane, whereas a pure Al2O3/SiO2 membrane does not show H2O2 sensing. A simulation based on Schottky, hopping, and Fowler-Nordheim tunneling conduction, and a redox reaction, is proposed. The experimental I-V curve matches very well with simulation. The resistive switching mechanism is owing to O-2(-) ion migration, and the redox reaction of Ir3+/Ir4+ at the IrOx/Al2O3 interface through H2O2 sensing as well as Schottky barrier height modulation is responsible. Glucose at a low concentration of 10 pM is detected using a completely new process in the IrOx/Al2O3/W cross-point structure. Therefore, this cross-point memory shows a method for low cost, scalable, memory with low current, multi-level operation, which will be useful for future highly dense three-dimensional (3D) memory and as a bio-sensor for the future diagnosis of human diseases.