Threshold Point Modulation of a Wake-Up Nano-Gap Gas Sensor

This paper reports the successful demonstration of modulating the threshold point in gas concentrations at which a gas sensor turns “on/of” for wake-up operation by adjusting the tunneling areas of a nano-gap in the previously reported ultra-low-power gas sensor. The nano-gap area of the sensor determines the total binding sites and thus the total amounts of “on” tunneling-current at a given concentration. Since the total current amounts trigger wake-up, their increase per given concentration could enable a lower minimum detectable wake-up concentration. Experimental results confirmed that the increase in the nano-gap area from 6.5 to
$62.5\ \mu \mathrm{m}^{2}$
by 861.5% enabled the reduction in the required wake-up gas concentrations from 250.0 to 50.0 ppm by 80.0%, showing an exponential decay trend. Such a reduction in the wakeup threshold allows the previously-reported sensor to achieve the required wake-up range of 200.0 ppm for early detection of diamine gases for health safety, while indicating the design feasibility to enable various wake-up concentrations for adjustable operation.