We have investigated the adsorption of lead phthalocyanine (PbPc) layers on GaAs$\left(001\right)$-$c(4\times 4)$ and $(2\times 4)$ reconstructed surfaces. Samples with different PbPc coverages from submonolayers up to $\approx$20-nm-thick layers were prepared under ultra-high vacuum conditions and investigated by scanning tunneling microscopy (STM) and reflectance anisotropy spectroscopy (RAS). The STM measurements showed different adsorption geometries of the PbPc molecules on the different reconstructions. The RAS results revealed that these different adsorption geometries in the first monolayer induce different molecular arrangements within thicker adsorbed layers on the two different substrates. These results give strong evidence for an epitaxial-like growth mode of PbPc molecules on GaAs$\left(001\right)$ surfaces driven by the atomic arrangement of the GaAs surface. We could also demonstrate RAS as a powerful tool to analyze the growth behavior of thin organic layers.

• Received 31 July 2011

DOI:https://doi.org/10.1103/PhysRevB.84.205317