Extended Data Fig. 7: Single Ag atoms on Ag(111)/Nb(110).

a, Constant-current STM image of a clean Ag area. The white bar corresponds to 10 nm. b–e, The same area after approaching the tip by 600 pm towards the surface at different positions. A single adsorbate of similar apparent height is found after each approach with the tip, consistent with the finding of ref. ⁵⁵. Therefore, we identify these adsorbates as single Ag atoms. f, Constant-current STM image of a QD’s wall consisting of Ag atoms manipulated to form a suitable shape of the wall. The white bar corresponds to 2 nm. g, dI/dV spectra measured on three of the Ag atoms marked in panel f (yellow, purple and red) as well as on the surface between the atoms (grey). Parameters: V = 15 mV, I = 1 nA for panels a–e; V = 5 mV, I = 1 nA for panel f; V_stab = −5 mV, I_stab = 1 nA, V_mod = 50 µV for panel g.