Figure 1

(Color online) (a) STM topographic image of the PTCDI/melamine network self-assembled on the $\text{Ag}/\text{Si}\left(111\right)\text{−}\surd 3\times \surd 3R30°$ surface ($V_{\text{s}}=-2.0\text{V}$, $I_{\text{t}}=75\text{pA}$, and $T=77\text{K}$). The dotted line indicates the position of a boundary line between two surface domains. [(i)–(iv)] Locations where the $dI/dV$ spectra shown in Fig. 2a were obtained. (b) Schematic diagram of the supramolecular structure superimposed to the STM view of a pore. The hexagonal mesh represents the substrate reconstruction, with the centers of the hexagons corresponding to the silicon trimer positions. (c) High-resolution STM view of the molecular network, where the Ag/Si(111) surface reconstruction is visible in the cavities ($V_{\text{s}}=-1.0\text{V}$, $I_{\text{t}}=75\text{pA}$, and $T=77\text{K}$). Scale bar 1.5 nm.Reuse & Permissions

Figure 2

(Color online) (a) $d\text{ln}\left(I\right)/d\text{ln}\left(V\right)$ normalized conductance curves obtained from the average of spectra measured on the bare surface (i and ${\text{i}}^{\prime }$), in the cavities (ii), on melamine molecules (iii), and on PTCDI molecules (iv) at a temperature of 77 K. The feedback conditions were sample voltage $V_{\text{s}}=-3\text{V}$ and tunneling current $I_{\text{t}}=0.1\text{nA}$, except for spectrum $\left({\text{i}}^{\prime }\right)$, which was acquired at $V_{\text{s}}=2.0\text{V}$ and $I_{\text{t}}=300\text{pA}$, with a variable tip-sample distance. The empty band of states in the Si band gap is labeled ${\text{S}}_1$. The spectra are shifted for clarity. Inset: $dI/dV$ map with $V_{\text{s}}=-0.5\text{V}$ showing the hybridized LUMO states of five PTCDI molecules. (b) STM topographic image of a cavity ($V_{\text{s}}=-3.0\text{V}$, $I_{\text{t}}=100\text{pA}$, and $T=77\text{K}$) and [(c) and (d)] simultaneously acquired $dI/dV$ maps with $V_{\text{s}}=+1.85\text{V}$ and $V_{\text{s}}=+2.55\text{V}$. Scale bar 1.5 nm.Reuse & Permissions

Figure 3

(a) Band structure of the inequivalent triangle model of $\text{Ag}/\text{Si}\left(111\right)\text{−}\surd 3\times \surd 3$, calculated with density-functional theory. The size of the circles denotes surface Ag character. The Fermi level is set to zero. Inset: corresponding density of surface Ag states. (b) Tight-binding band structure obtained for a simple hexagonal Ag lattice. [(c) and (d)] Detail of tight-binding band structure for a hexagonal Ag lattice covered with a hexagonal array of potential barriers representing the PTDCI and melamine molecular network. The barrier is set to zero in (c) and to 0.25 eV in (d). Dotted lines indicate energies at which several bands are clustered near the M and K points. Note that the Brillouin zone in (c) and (d) is smaller, by a factor $3\surd 3\times 3\surd 3$, than in (a) and (b); for clarity they are displayed here on the same scale. (e) Calculated density of states for the bare Ag/Si(111) surface, in the center of the molecular cavity and at the position of both types of molecules.Reuse & Permissions

Figure 4

(Color online) (a) Schematic model of the Ag/Si lattice showing the locations (black circles) of potential barriers used to represent the PTCDI and melamine molecules. The barrier height was set to 0.25 eV. The scale bar is 1.5 nm. [(b) and (c)] Calculated probability densities at energies of $+1.9$ and $+2.4\text{eV}$. (d) Electronic density of states of the melamine (solid line) and PTCDI (dotted line) molecules adsorbed on the Ag/Si surface. Inset: electron-density isosurface for states between 2.57 and 2.60 eV.Reuse & Permissions

Figure 5

(Color online) (a) Schematic diagram showing the registry of the PTCDI-melamine molecular complex with the Ag(111) surface. [(b) and (c)] Difference of the surface potential between the Ag(111) surface after the adsorption of the PTCDI/melamine complex and the bare Ag (111) surface. The potential profile has been, respectively, obtained along the main axis of the molecular complex and along a segment that runs perpendicular to this axis, as pointed out by the arrows in (a). The mean potential barrier, drawn as a strong line, has been calculated in the three regions defined by the dotted lines.Reuse & Permissions