Figures from "Direct observation of oriented molecular adsorption at step edges: a cryogenic scanning tunneling microscopy study", by E.R. Frank, X.X. Chen, and R.J. Hamers, Surface Science vol. 334, p. L709-L714(1995)
Figure 1Structural drawing of the molecules used in this study
Figure 2
a) 0.5 L 2,2'-bithiophene on Ag(111) imaged at 120 K. Adsorption occurs preferentially along step edges. The molecule has a preferred rotational orientation with the long molecular axis aligned parallel to the step direction. Tunneling conditions: I=40 pA, Vsamp = -2.1 V, image dimensions: 80 angstroms X 50 angstroms
(b) Height profile across 2,2'-bithiophene molecules adsorbed on step edges.
Figure 3
High coverages of 2,2'-bithiophene on Ag(111).
(a) A disordered area showing several molecular orientations. Image size: 80 angstroms X 80 angstroms.
(b) An ordered area of (4 X ) symmetry. A domain boundary runs through the center of the image. Image dimensions: 150 angstroms X 150 angstroms
Figure 4
STM images of two related molecules at 120 K on Ag(111).
(a) STM image of thiophene, showing adsorption at step edges and circular appearance.
(b)STM image of 2,5-dimethylthiophene showing adsorption at step edge and elongation of molecule perpendicular to step edge.
Last updated August 9, 1996