title: Energy-Level Alignment for Single-Molecule Conductance of Extended Metal-Atom Chains.
abstract: The use of single-molecule junctions for various functions constitutes a central goal of molecular electronics. The functional features and the efficiency of electron transport are dictated by the degree of energy-level alignment (ELA), that is, the offset potential between the electrode Fermi level and the frontier molecular orbitals. Examples manifesting ELA are rare owing to experimental challenges and the large energy barriers of typical model compounds. In this work, single-molecule junctions of organometallic compounds with five metal centers joined in a collinear fashion were analyzed. The single-molecule i-V scans could be conducted in a reliable manner, and the EFMO levels were electrochemically accessible. When the electrode Fermi level (EF ) is close to the frontier orbitals (EFMO ) of the bridging molecule, larger conductance was observed. The smaller |EF -EFMO | gap was also derived quantitatively, unambiguously confirming the ELA. The mechanism is described in terms of a two-level model involving co-tunneling and sequential tunneling processes.
authors.affiliation: Department of Chemistry and Center for Emerging Material and Advanced Device, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei, 10617 (Taiwan).
authors.forename: Ta-Cheng
authors.initials: TC
authors.lastname: Ting
authors.affiliation: Department of Chemistry and Center for Emerging Material and Advanced Device, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei, 10617 (Taiwan).
authors.forename: Liang-Yan
authors.initials: LY
authors.lastname: Hsu
authors.affiliation: Department of Chemistry and Center for Emerging Material and Advanced Device, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei, 10617 (Taiwan).
authors.forename: Min-Jie
authors.initials: MJ
authors.lastname: Huang
authors.affiliation: Department of Chemistry and Center for Emerging Material and Advanced Device, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei, 10617 (Taiwan).
authors.forename: Er-Chien
authors.initials: EC
authors.lastname: Horng
authors.affiliation: Department of Chemistry and Center for Emerging Material and Advanced Device, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei, 10617 (Taiwan).
authors.forename: Hao-Cheng
authors.initials: HC
authors.lastname: Lu
authors.affiliation: Department of Chemistry and Center for Emerging Material and Advanced Device, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei, 10617 (Taiwan).
authors.forename: Chan-Hsiang
authors.initials: CH
authors.lastname: Hsu
authors.affiliation: Department of Chemistry and Center for Emerging Material and Advanced Device, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei, 10617 (Taiwan).
authors.forename: Ching-Hong
authors.initials: CH
authors.lastname: Jiang
authors.affiliation: Department of Chemistry and Center for Emerging Material and Advanced Device, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei, 10617 (Taiwan). byjin@ntu.edu.tw.
authors.forename: Bih-Yaw
authors.initials: BY
authors.lastname: Jin
authors.affiliation: Department of Chemistry and Center for Emerging Material and Advanced Device, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei, 10617 (Taiwan). smpeng@ntu.edu.tw.|Institute of Chemistry, Academia Sinica, Taipei, 11529 (Taiwan). smpeng@ntu.edu.tw.
authors.forename: Shie-Ming
authors.initials: SM
authors.lastname: Peng
authors.affiliation: Department of Chemistry and Center for Emerging Material and Advanced Device, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei, 10617 (Taiwan). chhchen@ntu.edu.tw.
authors.forename: Chun-Hsien
authors.initials: CH
authors.lastname: Chen
keywords: electrochemistry; electron transfer; molecular junctions; scanning tunneling microscopy