Figure 1

(a) Topographic STM image of $5\times 2$ recorded simultaneously with the spectroscopic data in (b) and (c). The chains are aligned horizontally. (b) $dI/dV$ map at $V_{\mathrm{sample}}=-1.03\mathrm{V}$. Long adatom-free sections (AFS) appear bright indicating high density of states. (c) $dI/dV$ map at $V_{\mathrm{sample}}=-1.19\mathrm{V}$. Long AFS appear dark indicating low density of states. Different appearance of long and short AFS within each map is caused by an energetic shift of the local electronic structure (see Fig. 2).Reuse & Permissions

Figure 2

(a) STS spectra as a function of location along the chains. Horizontal dashed lines correspond to the positions of peak $A$ in the $dI/dV$ curves [cf. Fig. 2b]. The locations of the adatoms are marked by blue circles. (b) STS spectra for an extended energy range measured at the locations indicated by triangles in (a). The length of the corresponding AFS is $l_s=12$ ($l_s=8$) for the red (black) curve. The dashed spectrum represents the $l_s=8$ case but is shifted horizontally by 72 mV for better comparison to the red curve. The five pronounced peaks are labeled $A\mathrm{\text{−}}E$. They essentially correspond to band edges, which shift relative to the Fermi level due to a change in the band filling. That, in turn, is caused by charge transfer from the two dopant atoms terminating an adatom-free section.Reuse & Permissions

Figure 3

(a) $dI/dV$ spectra at the center of AFS, each of them averaged over several sections of same lengths $l_s$ (given in units of a bulk Si-Si distance along the chain $a_{\mathrm{Si}}$). Curves are offset vertically for clarity. Arrows indicate voltages for the $dI/dV$ maps in Figs. 1b, 1c. The continuous downward shift for decreasing $l_s$ is caused by an increase in local carrier concentration and the interaction with the charged dopands. (b) Peak position as a function of inverse adatom distance (bottom axis) and electron concentration (top axis) within the AFS. Solid circles: raw data; open circles: after correction for the Coulomb interaction with neighboring adatoms. The error bars reflect the standard deviation of results obtained from the different AFS. Inset: Peak position of state $A$ obtained from a Gaussian fit from (a).Reuse & Permissions

Figure 4

Measured energy position (circles) of state $A$ [see Fig. 2b] on an AFS ($l_s=16$) as a function of location along the chain. Blue solid curve: fit of a Coulomb-like potential induced by both adatoms. The dashed curves represent the two components of the individual adatoms located at $x=0$ and $x=16$, respectively.Reuse & Permissions