Fig. 2: Current as a function of tip height for ZnPc adsorbed on NaCl films of different thicknesses on Au(111).
From: Charge-state lifetimes of single molecules on few monolayers of NaCl
I(z) spectroscopy at the (a) negative ion resonance (NIR) and (b) positive ion resonance (PIR) of ZnPc molecules adsorbed on 3–5 monolayer (ML) NaCl/Au(111). Fits to the data are shown in red. On 3 ML at NIR, the molecule dislocated at z ≈ −4.8 Å, resulting in an abrupt change in current. The insets in a and b exemplify the lateral position of the tip, atop regions of high orbital density, during the spectra. c Constant-height STM images (V = −1.2 V) of ZnPc adsorbed on 5 ML NaCl/Au(111) recorded at different tip-sample distances. The tip-height offset Δz is given with respect to the STM setpoint of V = −1.2 V, I = 0.5 pA above the bare NaCl surface. The scale bar corresponds to 1 nm and applies to all images in c. d Line profiles along the dashed colored lines indicated in c. e, f dI/dV as a function of V of H2Pc adsorbed on 4 ML NaCl on Cu(111) (setpoint V = 1.6 V, I = 0.5 pA, Δz = −1 Å) e and 3 ML NaCl on Au(111) (setpoint V = 2 V, I = 0.5 pA, Δz = −1 Å); obtained by numerical differentiation of constant-height I(V)-curves.
