Π Band Dispersion along Conjugated Organic Nanowires Synthesized on a Metal Oxide Semiconductor

Abstract

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 π 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.

Small bandgap in atomically precise 17-atom-wide armchair-edged graphene nanoribbons

“…In particular, the bottom-up synthesis of N-AGNRs (where N is the width measured by the number of rows of carbon atoms across the AGNRs) has been widely conducted because the bandgap of AGNRs can be tuned by changing their width. Following the pioneering work on 7-AGNR on Au(111) 12 , various N-AGNRs have been reported, such as 3-AGNR 16,17 , 5-AGNR 18 , 9-AGNR 19 , and 13-AGNR 20 , as well as the fused AGNRs prepared by cyclodehydrogenation along the edge direction (e.g., 14-AGNR, 18-AGNR, and 21-AGNRs) 21,22 .…”

The Orientation of Silver Surfaces Drives the Reactivity and the Selectivity in Homo‐Coupling Reactions

“…This issue also affects the C=O related features in XPS: an overall broadening is observed for the O 1 s spectrum as well as for the high BE component of the C 1 s spectrum. An important expected effect of the polymerization would be the delocalization of the electronic states near the Fermi level . HREELS spectra were thus recorded for higher energy losses (see SI Figure S4) and indeed revealed a bathochromic effect, indicative of a reduction of the HOMO‐LUMO gap ,…”

Angle-Resolved Photoemission Study on the Band Structure of Organic Single Crystals

“…A substantial amount of ARPES measurements have been carried out on highly ordered organic monolayers or a few layers grown on non-reactive substrates [8,[24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43]. There has been a comprehensive review on these ARPES measurements [8].…”