|I|–V-curves taken fromz= 4.9 nm (bright red curve) to 6.7 nm (dark red curve) in steps of Δz= 0.3 nm. At negative bias, the onset current remains approximately constant. In stark contrast, the onset current at positive bias reduces exponentially. Note that the onset current at negative bias (I≈ −20 pA) slightly increases resulting in constant linear conductance.
