High frequency clipper like behavior of tri-layer nickel oxide stack
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(a). Typical input and output characteristics for 1 V signal of frequencies 1 MHz, where the blue line indicates the input signal and the red line indicates output signal. Inset shows schematic diagram of measurement setup and device structure of stack A. The input signal was passed from FG to the sample through Ni and the output signal was collected by OS. The variation in output signal with respect to input signal was observed in real time by comparing signal from input reference that carried the input signal directly from FG to OS. (b). The input voltage vs output voltage of signal frequencies are 20 kHz, 50 kHz, 100 kHz, 500 kHz, and 1 MHz, respectively, where dashed arrows show clipping voltage (Vc) at 0.82 V for 100 kHz and 0.65 V for 1 MHz signals, respectively, and solid arrows indicate direction of AC cycle. (c). AC characteristics of stack B and at 1 MHz under 1 V input. The inset shows the plot of input voltage vs output voltage where Vc is 0.4 V and the stack structure. (d). AC characteristics of stack C at 1 MHz, 1 V input signal. The inset shows the device structure.
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(a) Current-voltage (I-V) characterization of stacks A, B, and C where voltage was cycled between 1 V and −1 V starting from 0 V and arrows indicate direction of voltage cycle. Plot A represents I-V of stack A, plot B for stack B, and plot C for stack C. Inset shows the schematic of measurement setup. (b). Log I-log V plots for stacks A, B, and C showing Ohmic conduction in region I and SCLC in region II. Linear fit of data for region I is shown by a blue line and that for region II by a red line. The slopes of these linear fit to data are shown on each plot for each film. The cross over region of Ohmic conduction to SCLC is marked by a circle around 150 mV.
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Proposed schematic explanation for AC and DC characteristics of tri-layer NiO, NiO(10%)/NiO(33%)/NiO(100%), where (+) indicates excess of Ni, (−) for nickel vacancies, e− represents electrons, and arrows indicate direction of electron flow. (a). Cross section of the stacked film when no signal is applied. (b). Electrons injected to NiO(10%) conduct Ohmically to NiO(100%) for input signal voltage <200 mV. (c). When the input signal voltage is between 200 mV and 5 V, the number of electrons injected into the NiO(10%) region is more than the number of electrons flowing out from the device thereby forming an electron buildup at the interface called space charge. (d). Above 5 V peak voltage, the electric field is high enough for opening up new conduction channels to dissipate space charge from the interface.
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