(a) An STM image of monolayer cyclohexane on the clean Rh(111) surface. The sample bias (Vs), tunneling current (It), and sample temperature (Ts) were 0.53 V, 0.19 nA, and 95 K, respectively. The unit cell of the superstructure is indicated by a blue rhombus. The dashed lines in the figure show the domain boundaries of the superstructure. (b) A line profile along the white line (A-B) in (a).
(a) A close-up STM image of the superstructure (Vs = 0.53 V, It = 0.19 nA, and Ts = 97 K). The images of molecules at the atop, hollow, and near-bridge sites are denoted by A, H, and B, respectively. (b) An adsorption model for the observed superstructure in (a). The positions of surface Rh atoms and cyclohexane molecules are illustrated by large circles and red dots, respectively. The unit cell of the superstructure is indicated by dashed lines. Adsorption geometries of molecules at the hollow sites are illustrated by black lines with the free CH2 groups (filled circles) and the softened C–H groups pointing to the surface (open circles).
(a) An STM image of cyclohexane adsorbed on the hydrogen-saturated Rh(111) surface (Vs = 0.63 V, It = 0.09 nA, and Ts = 97 K). (b) A line profile along the white line (A-B) in (a).
Rh 3d5/2 spectra of (a) clean Rh(111), (b) cyclohexane adsorbed Rh(111), (c) hydrogen-saturated Rh(111) (H/Rh(111)), and (d) cyclohexane adsorbed H/Rh(111) (hν = 380 eV, Ts = 90 K). The spectra were fitted assuming bulk and surface components.
C 1s spectra of adsorbed cyclohexane on (a) the clean and (b) the hydrogen-saturated Rh(111) surfaces (hν = 380 eV, Ts = 90 K). The fitting results are also shown.
(a) UPS spectra of the clean and the hydrogen-saturated Rh(111) surfaces. (b) UPS spectra of multilayer cyclohexane (top), monolayer cyclohexane on the clean Rh (111) (middle), and monolayer cyclohexane on the hydrogen-saturated Rh(111) (bottom) using the HeI light source (Ts = 90 K). (c) Closeup of the UPS spectra of multilayer and monolayer cyclohexane on the clean Rh(111) surface. The lower BE components in the valence orbitals of monolayer cyclohexane are indicated by arrows.
(a) A summary of UPS and XPS results of cyclohexane on the clean (left) and the hydrogen-saturated (right) Rh(111) surfaces. (b) A schematic illustration of the effects of the vacuum level (VL) shift and the final-state screening on the energy level alignment of cyclohexane. The estimated C 1s BEs by taking into account these two factors are also shown in eV. The cyclohexane LUMO level is indicated by dotted lines (absolute energy position is uncertain). The ionization energy of cyclohexane (290.12 eV) is taken from Ref. 29 . The VL shifts were estimated from the experimental work function change (Fig. 6 ). The screening effects (Escr) were calculated assuming the image charge screening by the substrate and the polarization screening by nearest neighbor molecules in the ordered cyclohexane layers.
Estimated polarization screening energy by neighboring molecules (Ep), image charge screening energy by the substrate (Emetal), and total screening energy (Escr = Ep + Emetal).
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