T. Schmitz-hubsch et al., Structure of 3,4,9,10-perylene-tetracarboxylic-dianhydride grown on reconstructed and unreconstructed Au(100), SURF SCI, 437(1-2), 1999, pp. 163-172
The growth of 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) has bee
n characterized on Au(100) from the submonolayer range to multilayer films
by scanning tunneling microscopy (STM) in ultrahigh vacuum (UHV) and under
ambient conditions. Two different structures of PTCDA are found, one of whi
ch is the well-known herringbone structure, with the plane of the molecule
flat-lying on the substrate surface. This structure is point-online coincid
ent with the Au( 100) lattice. The second structure which is predominant on
this surface consists of closely spaced rods, each rod consisting of close
ly packed PTCDA molecules. We propose that this structure is associated wit
h the (010) bulk plane of the alpha-polymorph of PTCDA. The reason for the
different growth behavior compared to PTCDA on Au(111) at the very same gro
wth conditions can be found in the nanoscopic structure of the reconstructe
d Au(100)(hex) surface. This reconstruction of the Au(100) surface provides
trenches along the Au[011] azimuth which act as a specific adsorption site
for PTCDA, leading to very low diffusion rates of this molecule following
its deposition. The diffusion rate of first-deposited PTCDA was low enough
to enable us to image single molecules at room temperature. These findings,
in comparison with results on the reconstructed Au(111) surface, show that
not only the substrate material and the symmetry, but also the surface str
ucture on the nanoscopic scale can rule the growth of the organic overlayer
. (C) 1999 Elsevier Science B.V. All rights reserved.