Electric Field Control of Molecular Charge State in a Single-Component 2D Organic Nanoarray

Dhaneesh Kumar, Cornelius Krull, Yuefeng Yin, Nikhil V. Medhekar, Agustin Schiffrin

Research output: Contribution to journalArticleResearchpeer-review

1 Citation (Scopus)

Abstract

Quantum dots (QD) with electric-field-controlled charge state are promising for electronics applications, e.g., digital information storage, single-electron transistors, and quantum computing. Inorganic QDs consisting of semiconductor nanostructures or heterostructures often offer limited control on size and composition distribution as well as low potential for scalability and/or nanoscale miniaturization. Owing to their tunability and self-assembly capability, using organic molecules as building nanounits can allow for bottom-up synthesis of two-dimensional (2D) nanoarrays of QDs. However, 2D molecular self-assembly protocols are often applicable on metals surfaces, where electronic hybridization and Fermi level pinning can hinder electric-field control of the QD charge state. Here, we demonstrate the synthesis of a single-component self-assembled 2D array of molecules [9,10-dicyanoanthracene (DCA)] that exhibit electric-field-controlled spatially periodic charging on a noble metal surface, Ag(111). The charge state of DCA can be altered (between neutral and negative), depending on its adsorption site, by the local electric field induced by a scanning tunneling microscope tip. Limited metal-molecule interactions result in an effective tunneling barrier between DCA and Ag(111) that enables electric-field-induced electron population of the lowest unoccupied molecular orbital (LUMO) and, hence, charging of the molecule. Subtle site-dependent variation of the molecular adsorption height translates into a significant spatial modulation of the molecular polarizability, dielectric constant, and LUMO energy level alignment, giving rise to a spatially dependent effective molecule-surface tunneling barrier and likelihood of charging. This work offers potential for high-density 2D self-assembled nanoarrays of identical QDs whose charge states can be addressed individually with an electric field.

Original languageEnglish
Pages (from-to)11882–11890
Number of pages9
JournalACS Nano
Volume13
Issue number10
DOIs
Publication statusPublished - 4 Oct 2019

Keywords

  • density functional theory
  • double-barrier tunneling junction
  • low-dimensional nanostructures
  • noncontact atomic force microscopy
  • organic quantum dots
  • scanning tunneling microscopy and spectroscopy
  • supramolecular self-assembly

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