Organic beam epitaxy using controlled PMDA-ODA coupling reactions on Cu{110}

Reflection-absorption infrared spectroscopy (RAIRS) has been used to study in detail, as a function of temperature and coverage, the interaction of pyromellitic dianhydride (PMDA) and 4,4-oxydianiline (ODA) on the clean and oxygen-precovered Cu{110} surfaces. On the clean surface, both molecules show coverage-dependent reorientation from flat lying to upright species. The adsorption of PMDA on the clean surface leads to a ring-opening reaction of one of the anhydride group to produce a. species with both carbonyl and carboxylate groups. The carbonyl group is lost into the gas phase above 350 K. with the resulting anhydride species bonded to the surface via the carboxylate group. The presence of preadsorbed oxygen also leads to the reaction of one of the anhydride soups, although in this case a dicarboxylate (phthalate) anhydride species is produced. The condensation reaction of 4,4-oxydianiline with the two PMDA-derived species has also been studied. It is shown that the PMDA-ODA oligomer can be grown layer by layer using controlled imide coupling reactions. The growth is monitored by IR spectroscopy.