(a) IV characteristics (125 μm × 125 μm top electrode). The black line in the positive bias shows a transition from OFF to ON state. The gray line shows a full ON state afterwards. The gray line in the negative bias shows a transition from ON to OFF state and the black line shows a full OFF state afterwards. Inset: Logarithmic representation. (b) Device schematic. (c) ON and OFF states dependence on increasing temperature. (d) Switching cycles using voltage pulses of +20, −20, and +2 V for setting, resetting and reading, respectively. (e) IV characteristics for device with poly-Si top contact (30 at. % excess Si, 37 nm thick layer, 125 μm × 125 μm contact size).
(a) Unipolar switching for device with ITO contact (250 μm × 250 μm contact size) (b) Unipolar programming with −8 V (set), −12 V (reset), and −1 V (read), (c) IV characteristics (125 μm × 125 μm top electrode).
(a) IV curve (in positive bias) shows three distinct levels (two set processes and competing process) (b) IV curve (in negative bias) shows three distinct levels (two reset processes and competing process).
Current-time graphs under a constant voltage bias of (a) −8 V and (b) −10 V.
Cole − Cole plots with equivalent circuits under 1 V in (a) OFF state and (b) ON state. Trap assisted tunneling fit in (c) ON (low resistance) state and (d) OFF (high resistance) state (Inset: Fowler-Nordheim tunneling fit in OFF state).
(a) STM I/V curves for the edge point (b) atomic force microscopy scan of the surface top side showing surface features attributed to the tops of growth columns (c) Scanning tunneling microscopy scan of a sample surface [different area to that in (b)] showing enhanced conductivity at column edges (d) Schematic of columnar structure of switching film and switchable site.
Schematic of one cycle process. (a) Initial OFF state before applying the electric field, showing as-grown silicon nanoinclusions nucleated at oxygen vacancy sites. (b) ON state after the chain formation, showing extra silicon nanoinclusions produced by field-driven migration of oxygen vacancies. (c) Annihilation process due to Joule heating. (d) Silicon and oxygen distribution at the weak point.
Different positions of switching point due to depletion of oxygen vacancies close to one interface (a) high resistive state: switching point near ITO/ poly-Si–SiOx interface; (b) high resistive state: switching point near SiOx − substrate interface; (c) low resistive state.
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