STM investigation of vapor-deposition polymerization

We present a study of vapor-deposition polymerization (VDP) to produce thin layers of poly(phenylquinoxaline) (PPQ), a material that can be used as an electron-transport layer in multilayer organic electroluminescent devices. The polymer is prepared by the thermally-induced polycondensation reaction of 1,3-bis(phenylglyoxaloyl)benzene and 3,3′-diaminobenzidine. The two monomers are deposited by evaporation onto an atomically clean Au(111) surface under ultrahigh-vacuum conditions. Polymer formation is monitored in situ by scanning tunneling microscopy. Photoluminscence (PL) spectroscopy measurements, performed in situ, reveal that the PL spectrum of the VDP product corresponds to a reference spectrum for solution-synthesized PPQ. For monolayer coverage, polymer clusters are formed with the chains oriented parallel to each other. STM images suggest that the VDP-prepared films can be much smoother and more uniform than films deposited by spin coating. © 2001 Elsevier Science B.V. All rights reserved.