Fig. 3: Electrical and optical evaluations.

a Current–voltage (I–V) characteristics of the fabricated NEM-NVM. At the sub-threshold region (\({{{{{\rm{V}}}}}}\)< \({{{{{{\rm{V}}}}}}}_{{{{{{\rm{program}}}}}}}\)), an ultralow off-state current of less than 100 fA was observed. The current curve increased abruptly at an applied voltage of 9.9 V (compliance current of 100 nA). b Contact resistance distribution represented by cumulative probability (total 100 devices). The blue circle represents the low contact resistance state (LCRS) of the programmed device, and the red circle represents the high contact resistance state (HCRS) of the unprogrammed device. The contact resistance was measured through the four-point probe method at one-half programming voltage with 100 nA compliance current. c Evaluation of the programming time. The voltage divider circuit is shown in the inset. The black line represents the bias pulse, and the blue line represents the divided voltage to the load resistor. The time difference between the bias pulse and divided voltage is the programming time (<110 ns). d Contact resistance with respect to the application of the voltage pulse. When an erase voltage pulse (0.9 V, 400 ns) was applied, the contact resistance increased abruptly, indicating a successful erase operation. e Surface profile images of three states (initial, programmed, and erased states) measured by high-resolution 3-dimensional laser scanning confocal microscope (scale bar = 500 nm).