Subhranu Samanta

Evolution of complementary resistive switching characteristics using IrOx/GdOx/Al2O3/TiN structure

The complementary resistive switching (CRS) characteristics using an IrOx/GdOx/Al2O3/TiN single cell are observed whereas the bipolar resistive switching (BRS) characteristics are observed for the IrOx/GdOx/TiN structure. Transmission electron microscope and energy dispersive X-ray spectroscopy depth profile show crystalline GdOx film and the presence of higher amount of oxygen at both IrOx/GdOx interface and Al2O3 layer. Inserting thin Al2O3 layer, the BRS is changed to CRS. This CRS has hopping distance of 0.58 nm and Poole-Frenkel current conductions for the “0” and “1” states, respectively. A schematic model using oxygen vacancy filament formation/rupture at the TE/GdOx interface and Al2O3 layer has been illustrated. This CRS device has good endurance of 1000 cycles with a pulse width of 1 μs, which is very useful for future crossbar architecture.

Understanding of multi-level resistive switching mechanism in GeO x through redox reaction in H 2 O 2 /sarcosine prostate cancer biomarker detection

Formation-free multi-level resistive switching characteristics by using 10 nm-thick polycrystalline GeOx film in a simple W/GeOx/W structure and understanding of switching mechanism through redox reaction in H2O2/sarcosine sensing (or changing Ge°/Ge4+ oxidation states under external bias) have been reported for the first time. Oxidation states of Ge0/Ge4+ are confirmed by both XPS and H2O2 sensing of GeOx membrane in electrolyte-insulator-semiconductor structure. Highly repeatable 1000 dc cycles and stable program/erase (P/E) endurance of >106 cycles at a small pulse width of 100 ns are achieved at a low operation current of 0.1 µA. The thickness of GeOx layer is found to be increased to 12.5 nm with the reduction of polycrystalline grain size of <7 nm after P/E of 106 cycles, which is observed by high-resolution TEM. The switching mechanism is explored through redox reaction in GeOx membrane by sensing 1 nM H2O2, which is owing to the change of oxidation states from Ge0 to Ge4+ because of the enhanced O2− ions migration in memory device under external bias. In addition, sarcosine as a prostate cancer biomarker with low concentration of 50 pM to 10 µM is also detected.