The preparation, orientation and electronic structure of poly(p-phenylenevinylene) (PPV) monolayers on silicon surfaces

Monolayers of poly(p-phenylenevinylene) (PPV) have been prepared on oxidized and hydrogen-terminated silicon surfaces. The hydrogen-terminated silicon surface was made by wet chemical treatment of Si{111}. The one monolayer film of an amphiphilic PPV precursor polymer was prepared with the Langmuir-Blodgett (LB) technique and thermally converted to PPV. Photoemission and X-ray absorption spectroscopy were used to follow the conversion process which is completed between 545 K and 575 K depending on the substrate. Valence level photoemission was also used to study the electronic structure of the polymer monolayer which is characterized by a conjugated π system. Additionally, X-ray absorption spectroscopy at the carbon K-edge showed that at least on oxidized silicon the polymer is oriented with its phenylene rings preferentially parallel to the surface.