G. Koller et al., Molecular architecture through substrate patterning: bithiophene on clean and sulphur patterned Ni(110), SURF SCI, 421(3), 1999, pp. 353-363
Here bithiophene monolayers formed on clean Ni(110) and the Ni(110) c(2x2)S
and p(4x1)S sulphur reconstructions are contrasted. Investigations with a
variety of techniques are presented with particular emphasis on angle-resol
ved ultra-violet photoemission spectroscopy and its ability to give informa
tion on the nature of the chemical bond and, through application of symmetr
y selection rules, the molecular orientation. On the clean Ni substrate the
bithiophene is strongly bound through the re orbitals, flat lying and diso
rdered. S modification passivates the substrates and turns off the pi inter
action. On the c(2 x 2)S substrate no strong preference for the molecular o
rientation is indicated. In contrast the p(4 x 1)S substrate's corrugated s
tructure acts as a template that forces the assembly of the molecular monol
ayer. This monolayer is ordered with the molecular axis parallel to the sub
strate ridges ([001] azimuth). The molecules adopt a syn-conformation, and
it is suggested that the sulphur atoms of both rings are involved in bondin
g to the Ni atoms exposed on the sides of the ridges of the reconstruction.
(C) 1999 Elsevier Science B.V. All rights reserved.