Fig. 5.

Theoretical analysis and computation. (A) Schematic energy diagram of the ECSTM showing the relative energy levels of the substrate, the tip, and the redox molecule. ε_FS and ε_FT denote the Fermi levels of the substrate and the tip, respectively; the energy levels of the redox molecule at the oxidized and reduced forms are represented by ε_ox and ε_red, respectively. (B) Dependence of STM tunneling current on the overpotential calculated by Eqs. 1-3 (see the text) with ρ_t = 0.42 and ρ_s = 0.29 number of states·eV^–1·atom^–1, α_t = α_s = 0.5, V_bias =–0.2 V, E_r = 0.45 eV, κ_S = 0.1, κ_t = 0.01, ξ = 0.7, γ = 0.20, θ = 5.6 eV^–1, ω_eff = 10¹³, T = 295 K, and other parameters with their normal values. The tunneling current is normalized relative to the maximum value.