Figure 1.

Set up for determining junction stiffness: A. An ac modulation applied to the PZT deflects it by an amount A₀. The modulation amplitude of the gap itself, A₀^GAP is different because of interaction forces in the tunnel junction. B. Imidazole-2-carboxamide. C. AC modulation of the PZT results in a corresponding modulation of the gap conductance that increases with the DC set-point current according to $G_{AC}={\beta A}_0^{\mathit{GAP}}{G}_{DC}$. D. Showing how the quantities G_AC and G_DC are extracted.