Figure 1

(Color online) (a) STM micrograph $(186\mathrm{\AA }\times 186\mathrm{\AA })$: $\mathrm{Ag}\left(111\right)$ atomic structure (left) and $\mathrm{PTCDA}∕\mathrm{Ag}\left(111\right)$ (right) at $10\mathrm{K}$. Scan direction: bottom to top (fast), left to right (slow). Marked scan line (arrow 1): scanning parameters were changed from $U=-10\mathrm{mV}$ (left) to $U=-1.5\mathrm{V}$ (right) at constant $I=6.6\mathrm{nA}$ (tip retraction from $\sim 3.0$ to $7.8\mathrm{\AA }$). Inset: $27\mathrm{\AA }\times 21\mathrm{\AA }$ region from (a) including fitted lattice lines, cf. text. (b) Image section as indicated by the white frame in (a), including Ag grid lines (red, green, blue/shades of gray). Experimental (left) and simulated (right) ($s$-tip) images, the latter inserted into the experimental image with maximum correlation (cf. text). Thin yellow (light gray) lines: $\mathrm{PTCDA}∕\mathrm{Ag}\left(111\right)$ supercell (Ref. 2). Red (dark gray) circles (radius $0.7\mathrm{\AA }$): molecule centers. Black dots: Ag positions underneath the simulated image. (c) Ball-and-stick model corresponding to (b), showing DFT-optimized adsorption sites. Schematic representations of free molecule LUMO and HOMO in blue (left) and green (right). White dots give centers of corresponding lobes. Shortest $\mathrm{O}\text{−}\mathrm{H}$ bridges are shown as solid (O on type A) and dotted lines (O on type B); details in text.Reuse & Permissions

Figure 2

(Color online) $\mathrm{PTCDA}∕\mathrm{Ag}\left(111\right)$: (a) Experimental (background-subtracted) and simulated $dI∕dV$ spectra, recorded on molecules of type A (red, full line) and B (blue, dashed line), cf. dots in (b). Tip height during STS: approx. $7.5\mathrm{\AA }$. Experimental spectra recorded with sensitized tip (Ref. 16) are shaded. Green (dash-dotted) spectrum: $\mathrm{Ag}\left(111\right)$. (c) $dI∕dV$ image recorded in the left flank of L1 ($I=1.8\mathrm{nA}$, modulation $288\mathrm{Hz}∕20\mathrm{meV}$). (d) Calculated free molecule HOMO.Reuse & Permissions

Figure 3

(Color online) $\mathrm{PTCDA}∕\mathrm{Ag}\left(111\right)$: (a–e) Experimental (right) and calculated (left) STM images ($23\mathrm{\AA }$ width). Experimental tip heights determined from current-distance curves. (f) Experimental and simulated corrugation as indicated by corresponding bars in (e).Reuse & Permissions