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(Color online) (a) Current-voltage characteristics of Ti-CuO-MLG-Cu sample during initial electroforming step showing transition to low resistance state (LRS) at forming voltage (VF) of −0.84 V with a current compliance limit (ICC) of 1 mA. Inset shows the schematic view of Ti-CuO-MLG-Cu structure. (b) I-V curve showing reversible and bipolar resistive switching in Ti-CuO-MLG-Cu sample under ambient condition. The sample switches from LRS to HRS at reset voltage (VR) of 0.48 V and switches back to LRS at set voltage (VS) of −0.68 V. The arrow indicates the sweep direction. (c) I-V characteristics showing the linear ohmic behavior with slope of about 0.99 and 0.94 in the LRS for the positive and negative bias region respectively in a double-logarithmic plot. Linearity is also observed in HRS at lower voltages with the slope of about 1.02 and 1.04 for both the regions. Deviation from the linearity is observed in HRS at higher voltages with the slope of about 1.98 and 1.96 for positive and negative regions respectively. (d) The endurance performance of the Ti-CuO-MLG-Cu based hybrid memory cell for about 100 cycles.
(Color online) I-V curve showing (a) the rectifying characteristics for Ti-CuO-Cu, (b) nearly linear behavior for Ti-MLG-Cu, and (c) non linear characteristics before electroforming for Ti-CuO-MLG-Cu junctions. (d) I-V curve showing reversible bipolar switching for Ti-CuO-MLG-Cu sample under 2.2 × 10−6 Torr vacuum. The sample switches from LRS to HRS atreset voltage (VR) of 0.07 V and switches back to LRS at set voltage (VS) of −0.63 V.
(Color online) (a) XPS C1s spectra in CuO-MLG and MLG samples after sputter time of 12 min. Additional C1s peak at higher energy is observed for CuO-MLG interfacial layer (IL). (b) O1s spectra showing two peaks in CuO and CuO-MLG sample correspond to the lattice oxygen and “non lattice” oxygen of CuO, and an additional peak for CuO-MLG interface is due to the oxygen species in MLG layer. (c) The Cu 2p spectra for CuO sample shows a single peak, whereas CuO-MLG sample shows two peaks, one correspond to the cupric phase and other corresponds to the formation of copper carbide at the interface. (d) Tabulated results for peak positions in C1s, O1s, and Cu2p spectra for CuO, MLG, and CuO-MLG interface.
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