Interfacial chemistry of perylene-3,4,9,10-tetracarboxylic dianhydride during the initial stages of film growth on InAs(1 1 1)A

X-ray photoelectron spectroscopy (XPS) and high resolution electron energy loss spectroscopy (HREELS) have been used to investigate the initial stages of film growth of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) on InAs(1 1 1)A substrates. XPS measurements show that the binding energies of the C 1s and O 1s core levels are considerably lower in sub-monolayer films compared to those observed in thicker films, suggesting significant charge transfer at the PTCDA/InAs interface. HREELS results at low film thickness also indicate some interaction as evidenced by a substantial red shift in the carbonyl stretching frequency of the molecules, although there is no molecular fragmentation. The results suggest that the PTCDA molecules in the first monolayer undergo significant interaction with the substrate, with charge transferred from the In-terminated surface to the carbonyl groups of the PTCDA molecules.