title: Thiophene-based Tripodal Anchor Units for Hole Transport in Single-Molecule Junctions with Gold Electrodes.
abstract: Molecule-metal junctions are inevitable for the realization of single-molecule electronics. In this study, we developed new tripodal anchors with electron-rich aromatic rings to achieve robust contact with gold electrodes, an effective hybridization of the π orbital with gold electrodes (π channel), and hole transport through π-channel hybridization. Cyclic voltammetry and X-ray photoelectron spectroscopy measurements of the monolayers indicated that the thiophene-based tripodal molecule exhibits anchoring characteristics as expected. The electrical conductance of thiophene-anchored bistripodal molecules using the scanning tunneling microscope (STM)-based break junction technique confirmed the formation of molecular junctions. The Seebeck coefficient of this compound estimated from thermoelectric voltage measurements using a STM was determined to be a positive value, which indicates that the charge carriers are holes. On the contrary, the corresponding pyridine-anchored molecules showed electron transport. These results reveal the versatility of π-channel tripodal anchors for the control of charge-carrier type in single-molecule electronics.
authors.affiliation: The Institute of Scientific and Industrial Research (ISIR), Osaka University , 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Ie
authors.affiliation: The Institute of Scientific and Industrial Research (ISIR), Osaka University , 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan.
authors.forename: Kazunari
authors.initials: K
authors.lastname: Tanaka
authors.affiliation: The Institute of Scientific and Industrial Research (ISIR), Osaka University , 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan.
authors.forename: Aya
authors.initials: A
authors.lastname: Tashiro
authors.affiliation: Graduate School of Engineering Science, Osaka University , 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan.
authors.forename: See Kei
authors.initials: SK
authors.lastname: Lee
authors.affiliation: Institute of Mechanical Engineering (IEM), Universidade Federal de Itajubá , 1303 Bairro Pinheirinho, Itajubá, Minas Gerais 37500 903, Brasil.
authors.forename: Henrique Rosa
authors.initials: HR
authors.lastname: Testai
authors.affiliation: Graduate School of Engineering Science, Osaka University , 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Yamada
authors.affiliation: Graduate School of Engineering Science, Osaka University , 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan.
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Tada
authors.affiliation: The Institute of Scientific and Industrial Research (ISIR), Osaka University , 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Aso
keywords: Seebeck coefficient; single-molecule electronics; single-molecule junction; structure−property relationship; surface analysis; tripodal anchor; π-channel hybridization