Surface Polymerization by Ion Assisted Deposition for Polythiophene Film Growth

Yongsoo Choi, Sanja Tepavcevic, and Luke Hanley

Department of Chemistry (mc 111)

University of Illinois at Chicago

Chicago, IL 60607-7061

www.chem.uic.edu/hanley

Abstract

Cationic polymerization is induced at the gas-solid interface by hyperthermal organic cations coincident on a surface with a thermal beam of organic monomers [1]. This process, termed surface polymerization by ion assisted deposition (SPIAD), produces films that maintain the chemical structure of the monomer [2]. A polythiophene film is produced here by SPIAD with 100 eV thiophene ions and terthiophene monomers coincident on Si and indium tin oxide (ITO) substrates held under vacuum. X-ray photoelectron spectroscopy observes enhancement in film growth for SPIAD compared with either thiophene ion or terthiophene exposure alone. Polythiophene films grown by both mass-selected [1] and non-mass-selected ions [3] with coincident terthiophene dosing both display similar fluorescence intensity at two wavelengths characteristic of emission from films of the terthiophene monomer. Raman spectra of films from non-mass-selected ions display several vibrations also observed in terthiophene films. Ions therefore play a critical role in film growth from non-mass-selected ions, in addition to any radical or photochemically driven processes that may also occur.

[1] L. Hanley and S.B. Sinnott, Surf. Sci. 500 (2002) 500.

[2] S. Tepavcevic, Y. Choi, and L. Hanley, J. Amer. Chem. Soc. 125 (2003) 2396.

[3] L. Hanley, Y. Choi, E.R. Fuoco, F.A. Akin, M.B.J. Wijesundara, M. Li, A. Tikhonov, and M. Schlossman, Nucl. Instr. Meth. Phys. Res. B (2003) in press.