REACTION OF ANILINE WITH CHEMISORBED PYROMELLITIC DIANHYDRIDE ON CU(110) - A MODEL FOR CONTROLLED ORGANIC FILM GROWTH

The reaction of aniline with pyromellitic dianhydride (PMDA) chemisorbed on Cu(110) has been followed by high-resolution electron energy-loss spectroscopy (EELS) and XPS. The PMDA is adsorbed via opening of one anhydride ring to permit a strong carboxylate link to the copper surface but with an unperturbed anhydride unit directed away from the substrate. The reaction with aniline takes place in a two-step process: formation of an amic acid intermediate; and loss of H2O with heating to 440 K, leading to the imide. The process demonstrated here is a model reaction that represents a successful initial step in the growth of complex, tailored, organic thin films by the sequential deposition/reaction of carefully selected bifunctional molecules, starting with a clean, well-defined, single-crystal substrate. One functionality of the molecule is used to bond to the growing film and the second provides the terminating surface ready to accept the next molecular layer.