Figure 1

(Color online) (a) and (b) typical empty state STM image of $\text{Si}\left(111\right)\text{−}\surd 3\times \surd 3\text{-Ga}$ surface at RT and 77 K, respectively. The positively charged Si dopant, appearing as depression in empty state, is denoted by a red arrow in (a). (c) Filled state STM image of 5 nm Ag film grown on $\text{Si}\left(111\right)\text{−}\surd 3\times \surd 3\text{-Ga}$ substrate at RT. The bright and less bright protrusions are denoted by white and black arrows, respectively. The black feature in the bottom-left of the image is due to a small angle grain boundary, which indicates a slight difference in the orientations of neighboring crystal domains, is consistent with the slightly streaky $\text{Ag-}1\times 1$ LEED spots [see Fig. 1e]. (d) Atomically resolved STM image of the protrusions in (c). The atomic structure of $\text{Ag}\left(111\right)\text{−}1\times 1$ is clearly resolved. (f) and (g) are the corresponding height distributions of the Si atoms in (b) and the bright protrusions in (c), respectively.Reuse & Permissions

Figure 2

(Color online) (a) Schematics showing how the dopant Coulomb potential can be imaged on top of the Ag films by the vertically confined electrons. Note that the lateral phase shift induced modulation of the surface charge density resembles the screened Coulomb potential at the interface. (b) An isolated dopant imaged on the Ag films surface. The inset shows the corresponding height profile. (c) and (d) tunneling spectra of 1.4 and 2.6 nm Ag films, respectively, obtained along the radial direction of the dopant image at positions equally spaced from point A to E, as shown in (b). The peaks of the QW resonances are indicated by arrows. The peak shift in (c) is guided for eyes by a dot line.Reuse & Permissions

Figure 3

(Color online) Schematics of the Ag/Si interface. $E_0$ is the valence band maximum of $\text{Si-}\surd 3\times \surd 3\text{-Ga}$ surface. The local band edge shift induced by the interfacial dopant potential is denoted by $\Delta V\left(x,y\right)$ (see the red dot line), which is equivalent with the variation in the Schottky barrier height $\left({\varphi }_{B,n}\right)$. The resulting reflection phase shift in the quantized electrons is denoted by $\Delta {\varphi }_s\left(x,y\right)$.Reuse & Permissions

Figure 4

(Color online) (a) The experimental height profile across one single dopant image on Ag films of 1.4 nm thick. The solid red line is a fit by Eq. (5). (b) and (c) the interface screening lengths $R_{\text{int}}$, extracted by fitting procedures, as functions of the sample bias $V$ and the film thickness $d$, respectively. The weighted averages of screening lengths are indicated by the horizontal dot red line.Reuse & Permissions