Figure 3. Current-voltage characteristic curves measured at different positions over the (a) H₂-TPP and (b) Co-TPP molecules absorbed on Cu₃Au (100) substrate.

The insets are STM images with the indication of the position were the curves were acquired. The STM topographic image were obtained at 0.30 V and 2.0 nA for both molecules. The I–V curves were obtained at a −0.55 V sample bias voltage and with a 2.0 nA set current for the H₂-TPP, while for Co-TPP the parameters are −0.60 V and 0.3 nA.