  Surface confined dehalogenation reactions are versatile bottom-up approaches
for the synthesis of carbon-based nanostructures with predefined chemical
properties. However, for devices generally requiring low conductivity
substrates, potential applications are so far severely hampered by the
necessity of a metallic surface to catalyze the reactions. In this work we
report the synthesis of ordered arrays of poly(p-phenylene) chains on the
surface of semiconducting TiO2(110) via a dehalogenative homocoupling of
4,4"-dibromoterphenyl precursors. The supramolecular phase is clearly
distinguished from the polymeric one using low energy electron diffraction and
scanning tunneling microscopy as the substrate temperature used for deposition
is varied. X ray photoelectron spectroscopy of C 1s and Br 3d core levels
traces the temperature of the onset of dehalogenation to around 475 K.
Moreover, angle-resolved photoemission spectroscopy and tight-binding
calculations identify a highly dispersive band characteristic of a substantial
overlap between the precursor's {\pi} states along the polymer, considered as
the fingerprint of a successful polymerization. Thus, these results establish
the first spectroscopic evidence that atomically precise carbon based
nanostructures can readily be synthesized on top of a transition-metal oxide
surface, opening the prospect for the bottom-up production of novel
molecule-semiconductor devices.
