Projects per year
Abstract
We report here an extensive study of transport and electronic structure of molecular junctions based on alkyl thiols (CnT; n = 7, 8, 9, 10, 12) and dithiols (CnDT; n = 8, 9, 10) with various lengths contacted with different metal electrodes (Ag, Au, Pt). The dependence of the low-bias resistance (R) on contact work function indicates that transport is HOMO-assisted (p-type transport). Analysis of the current-voltage (I-V) characteristics for CnT and CnDT tunnel junctions with the analytical single-level model (SLM) provides both the HOMO-Fermi energy offset h trans and the average molecule-electrode coupling (I") as a function of molecular length (n), electrode work function (φ), and the number of chemical contacts (one or two). The SLM analysis reveals a strong Fermi level (EF) pinning effect in all the junctions, i.e., h trans changes very little with n, φ, and the number of chemical contacts, but I" depends strongly on these variables. Significantly, independent measurements of the HOMO-Fermi level offset (h) by ultraviolet photoelectron spectroscopy (UPS) for CnT and CnDT SAMs agree remarkably well with the transport-estimated This result provides strong evidence for hole transport mediated by localized HOMO states at the Au-thiol interface, and not by the delocalized σ states in the C-C backbones, clarifying a long-standing issue in molecular electronics. Our results also substantiate the application of the single-level model for quantitative, unified understanding of transport in benchmark molecular junctions.
Original language | English (US) |
---|---|
Pages (from-to) | 18182-18192 |
Number of pages | 11 |
Journal | Journal of the American Chemical Society |
Volume | 141 |
Issue number | 45 |
DOIs | |
State | Published - Nov 13 2019 |
Bibliographical note
Funding Information:C.D.F. acknowledges financial support from the U.S. National Science Foundation (CHE-1708173). Parts of this work were carried out in the Characterization Facility, University of Minnesota, which receives partial support from the NSF through the MRSEC program. I.B. acknowledges financial support from the Deutsche Forschungsgemeinschaft (grant BA 1799/3-2) and computational support from the State of Baden-Württemberg through bwHPC and the German Research Foundation (DFG) through grant no. INST 40/467-1 FUGG. (80)
Publisher Copyright:
Copyright © 2019 American Chemical Society.
How much support was provided by MRSEC?
- Shared
Reporting period for MRSEC
- Period 6
PubMed: MeSH publication types
- Journal Article
Fingerprint
Dive into the research topics of 'Energy Level Alignment in Molecular Tunnel Junctions by Transport and Spectroscopy: Self-Consistency for the Case of Alkyl Thiols and Dithiols on Ag, Au, and Pt Electrodes'. Together they form a unique fingerprint.-
MRSEC IRG-1: Electrostatic Control of Materials
Leighton, C., Birol, T., Fernandes, R. M., Frisbie, D., Goldman, A. M., Greven, M., Jalan, B., Koester, S. J., He, T., Jeong, J. S., Koirala, S., Paul, A., Thoutam, L. R. & Yu, G.
9/1/98 → …
Project: Research project
-
MRSEC Program
THE NATIONAL SCIENCE FOUNDATION, UNIVERSITY OF TEXAS RIO GRANDE VALLEY
8/1/98 → 10/31/20
Project: Research project