Figure 1

(a) STM image ($200\times 200\mathrm{nm}$, $+0.3\mathrm{V}$, 0.025 nA) of submonolayer ${\mathrm{C}}_6{\mathrm{F}}_6$ deposited onto a Cu(111) surface held at 10 K. (b) Enlarged image of a fractal island ($27\times 27\mathrm{nm}$, $+0.2\mathrm{V}$, 0.1 nA) with specific molecules with 2, 4, and 6 NN indicated by colored dots, for which the $dz/dV$ measurements are performed. (c) An image of compact hexagonal ${\mathrm{C}}_6{\mathrm{F}}_6$ islands after annealing the sample to 80 K. The enlarged image in the inset shows the ($3\times 3$) overlayer structure and the surface unit cell with 0.77 nm dimensions.Reuse & Permissions

Figure 2

(a) Several $dz/dV$ spectra from isolated molecule to one monolayer coverage spanning the range of ${\mathrm{C}}_6{\mathrm{F}}_6$ aggregation for different numbers of nearest neighbors. (b) The experimentally observed stabilization energy relative to an isolated molecule from the data in (a). The theoretical stabilization energy is calculated by the tight binding model for fractal islands consisting of 28–66 molecules.Reuse & Permissions

Figure 3

(a) The radial distributions of the $\mathit{N}=(0-3,0,0)$ probability densities averaged over the azimuthal and surface normal coordinates, showing the increasing superatom character as $n_r$ is increased. The locations of C and F atoms are indicated. The characteristic properties of SAMOs include dominant non-nuclear probability density within the hollow ring and beyond the F atom perimeter, as well as density minima on C and F atoms. (b) The comparison of the probability densities of the superatom ${\sigma }^{*}$ LUMO, with the aromatic $\pi$ and ${\pi }^{*}$ HOMO and $\mathrm{LUMO}+1$. Unlike the ${\sigma }^{*}$ orbital, the $\pi$ orbitals are localized on C and F atoms. (c) The calculated band dispersions for HOMO, LUMO, and $\mathrm{LUMO}+1$. The $\pi$ ($m_{\mathrm{eff}}=-40m_e$) and ${\pi }^{*}$ ($m_{\mathrm{eff}}=-80m_e$) bands are essentially dispersionless, whereas ${\sigma }^{*}$ ($m_{\mathrm{eff}}=2m_e$) has NFE character. The orbital densities for the three bands contrast the large intermolecular density for ${\sigma }^{*}$ with the localized character of $\pi$ and ${\pi }^{*}$. Only one component of each doubly degenerate π orbitals is shown.Reuse & Permissions

Figure 4

The calculated energy level diagram and molecular orbitals of isolated ${\mathrm{C}}_6{\mathrm{F}}_6$. The energy distribution of the $n_r$, $l$, and $n_z$ quantum numbers is shown separately. Side and top views labeled by quantum numbers $\mathit{N}=(n_r,l,n_z)$ are shown for the orbitals in Figs. 3a, 3b.Reuse & Permissions