Vibrational properties of ordered perylene thin films on GaAs(1 0 0) and InAs(1 1 1)A

The growth of ordered perylene (Pe) thin films on GaAs(1 0 0) and InAs(1 1 1)A has been studied by high resolution electron energy loss spectroscopy (HREELS). Specular HREELS spectra recorded as a function of film thickness show differences in the monolayer regime when compared to multilayer Pe films, with many of the vibrational modes of the molecule showing significant changes in intensity. The results suggest that in the monolayer phase the molecules adopt an orientation that is parallel to the surface, whilst in the multilayer phase the vibrational spectra are consistent with a bulk-like Pe structure.