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 GeO(x) film in a simple W/GeO(x)/W structure and understanding of switching mechanism through redox reaction in H(2)O(2)/sarcosine sensing (or changing Ge°/Ge(4+) oxidation states under external bias) have been reported for the first time. Oxidation states of Ge(0)/Ge(4+) are confirmed by both XPS and H(2)O(2) sensing of GeO(x) membrane in electrolyte-insulator-semiconductor structure. Highly repeatable 1000 dc cycles and stable program/erase (P/E) endurance of >10(6) cycles at a small pulse width of 100 ns are achieved at a low operation current of 0.1 µA. The thickness of GeO(x) layer is found to be increased to 12.5 nm with the reduction of polycrystalline grain size of <7 nm after P/E of 10(6) cycles, which is observed by high-resolution TEM. The switching mechanism is explored through redox reaction in GeO(x) membrane by sensing 1 nM H(2)O(2), which is owing to the change of oxidation states from Ge(0) to Ge(4+) because of the enhanced O(2−) 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.