Fig. 5: Schematic representation of the working principle of the nanogap sensor, equivalent electrical model, and representative band diagram.
a Schematic of the nanogap device after fabrication and analyte capture. Successful target capture turns the switch ‘ON’. b Schematic representation of current conduction before and after analyte gas capture, and equivalent electrical model depicting the two current conducting paths. c Average edge energy barrier in the absence of a target analyte gas, and d average energy barrier at a molecular junction established by the capture of a target gas molecule. The average energy barrier is lowered, leading to a larger tunneling current. IS is the electric current through the dielectric spacer stack, and IE (Cg) is the net current through the molecular bridges formed due to target gas capture and is a function of the target gas concentration Cg. ΦE(0) and ΦE(Cg) are the average potentials barrier before and after the capture of the target gas, respectively. χtarget is the electron affinity of the captured target. ψSAM and ψAu are the work functions of the SAM layer and the metal layer, respectively
