title: Resolving band-structure evolution and defect-induced states of single conjugated oligomers by scanning tunneling microscopy and tight-binding calculations.
abstract: We study single conjugated polyphenylene oligomers consisting of 3n (2 ≤ n ≤ 12) phenyl units by means of cryogenic scanning tunneling microscopy and spectroscopy. The spatially resolved local densities of states reveal a progressive development of a continuous conduction band out of discrete molecular orbitals as the length of the oligomers increases. The experimental results are satisfactorily described by tight-binding calculations which gave a conduction band bandwidth of 4.5 ± 0.2 eV and a band gap of 3.1 ± 0.2 eV for an infinitely long polymer. We observed two types of defects, known as conformational torsional angle misfit and metasite kink. Tight-binding as well as density-functional theory model calculations confirm that both types of defects effectively destroy the delocalization.
authors.affiliation: Department of Physics, The Hong Kong University of Science and Technology, Hong Kong, China.
authors.forename: Shiyong
authors.initials: S
authors.lastname: Wang
authors.forename: Weihua
authors.initials: W
authors.lastname: Wang
authors.forename: Nian
authors.initials: N
authors.lastname: Lin