Cross-Point Resistive Switching Memory and Urea Sensing by Using Annealed GdOx Film in IrOx/GdOx/W Structure for Biomedical Applications

Resistive switching characteristics and urea sensing have been investigated by using annealed GdOx film in IrOx/GdOx/W cross-point memory for the first time. The annealed GdOx film shows larger polycrystalline grains as compared to as-deposited films, which is observed by high-resolution transmission electron microscope (HRTEM) and X-ray diffraction patterns (XRD). Surface roughness of the GdOx films on W nano-dome is observed by atomic force microscope (AFM). The annealed IrOx/GdOx/W cross-point memory shows resistance ratio of 1000x times higher, multi-level operation with varying current compliance (CC) from 10-300 mu A, good non-linearity factor of 8.3, good dc switching cycles of > 1000 at CC of 10 mu A, long read endurance of > 10(9) cycles with pulse width of 1 mu s at higher read voltage of -0.5 V, and high speed operation of 100 ns. Repeatable resistive switching characteristics at low CC of 10 mu A and mechanism are due to the electric field enhancement on the W nano-dome simulated by MATLAB, which controls the O2- ions migration through polycrystalline GdOx grain boundary as well as Schottky barrier height modulation (0.59 vs. 0.39 eV). In addition, the annealed GdOx membrane in electrolyte-insulator-semiconductor (EIS) structure shows higher pH sensitivity than the as-deposited film (53.2 vs. 45.1 mV/pH) and lower drift (1.8 vs. 2.6 mV/hr) as well as lower detection of pH change (0.034). Detection of pH and urea sensing from 6 to 24 mg/dl have been measured by using cross-point memory, and the sensing mechanism is also discussed, which will be very useful for real healthcare unit in near future. (C) The Author(s) 2017. Published by ECS.