Figures from "Spatially- and Rotationally-oriented Adsorption of Molecular Adsorbates on Ag(111) Investigated using Cryogenic Scanning Tunneling Microscopy", by X. Chen, E. R. Frank, and R. J. Hamers.

Figure 1

Molecular structures for thiophene and 2,5-dimethylthiophene(DMT)


Figure 2

Thiophene adsorption at Ag(111) step edges at different coverages.
(2a) 0.05 L exposure, showing that thiophene bonds only to upper step edges forming a nearly evenly spaced one dimensional molecular array.
(2b) 0.2 L exposure, showing additional molecules forming a partial second row on the upper terrace and "twins" on the lower terrace. Sample bias is -1.8 V, and tunneling current is 0.2 nA.


Figure 3

Schematic illustration of electrostatic interactions between step edge dipole and molecular dipole, as discussed in text.


Figure 4

STM image of 2,5-dimethylthiophene on Ag(111) step edges, showing elongated shape perpendicular to the step edge.
(4a) 0.5 L exposure
(4b) 0.05 L exposure, revealing molecular clustering along the step edge below saturation coverage.


Figure 5

Ab initio molecular orbital calculation of the interaction energy between thiophene molecules in a coplanar geometry described in text.

Figure 6

STM images showing thiophene molecules adsorbed on Ag(111) step edges with different crystallographic orientations.

Figure 7

STM images of Ag(111) exposed to thiophene at increasing coverage:
(7a) Exposure = 40 L, producing c(23x4)rect ordered overlayer
(7b) Exposure = 90 L, producing (27x27) structure
(7c) Exposure = 150 L, producing herringbone structure


Last updated February 2, 1998