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Title: Weak competing interactions control assembly of strongly bonded TCNQ ionic acceptor molecules on silver surfaces

Abstract

The energy scales of interactions that control molecular adsorption and assembly on surfaces can vary by several orders of magnitude, yet the importance of each contributing interaction is not apparent a priori. Tetracyanoquinodimethane (TCNQ) is an archetypal electron acceptor molecule and it is a key component of organic metals. On metal surfaces, this molecule also acts as an electron acceptor, producing negatively charged adsorbates. It is therefore rather intriguing to observe attractive molecular interactions in this system that were reported previously for copper and silver surfaces. In this paper, our experiments compared TCNQ adsorption on noble metal surfaces of Ag(100) and Ag(111). In both cases we found net attractive interactions down to the lowest coverage. However, the morphology of the assemblies was strikingly different, with two-dimensional islands on Ag(100) and one-dimensional chains on Ag(111) surfaces. This observation suggests that the registry effect governed by the molecular interaction with the underlying lattice potential is critical in determining the dimensionality of the molecular assembly. Using first-principles density functional calculations with a van der Waals correction scheme, we revealed that the strengths of major interactions (i.e., lattice potential corrugation, intermolecular attraction, and charge-transfer-induced repulsion) are all similar in energy. The van der Waalsmore » interactions, in particular, almost double the strength of attractive interactions, making the intermolecular potential comparable in strength to the diffusion potential and promoting self-assembly. However, it is the anisotropy of local intermolecular interactions that is primarily responsible for the difference in the topology of the molecular islands on Ag(100) and Ag(111) surfaces. Finally, we anticipate that the intermolecular potential will become more attractive and dominant over the diffusion potential with increasing molecular size, providing new design strategies for the structure and charge transfer within molecular layers.« less

Authors:
 [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE Laboratory Directed Research and Development (LDRD) Program
OSTI Identifier:
1337811
DOE Contract Number:  
AC05-00OR22725; AC02-05CH11231
Resource Type:
Journal Article
Journal Name:
Physical Review. B, Condensed Matter and Materials Physics
Additional Journal Information:
Journal Volume: 90; Journal Issue: 12; Journal ID: ISSN 1098-0121
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Park, Changwon, Rojas, Geoffrey A., Jeon, Seokmin, Kelly, Simon J., Smith, Sean C., Sumpter, Bobby G., Yoon, Mina, and Maksymovych, Petro. Weak competing interactions control assembly of strongly bonded TCNQ ionic acceptor molecules on silver surfaces. United States: N. p., 2014. Web. doi:10.1103/PhysRevB.90.125432.
Park, Changwon, Rojas, Geoffrey A., Jeon, Seokmin, Kelly, Simon J., Smith, Sean C., Sumpter, Bobby G., Yoon, Mina, & Maksymovych, Petro. Weak competing interactions control assembly of strongly bonded TCNQ ionic acceptor molecules on silver surfaces. United States. doi:10.1103/PhysRevB.90.125432.
Park, Changwon, Rojas, Geoffrey A., Jeon, Seokmin, Kelly, Simon J., Smith, Sean C., Sumpter, Bobby G., Yoon, Mina, and Maksymovych, Petro. Fri . "Weak competing interactions control assembly of strongly bonded TCNQ ionic acceptor molecules on silver surfaces". United States. doi:10.1103/PhysRevB.90.125432.
@article{osti_1337811,
title = {Weak competing interactions control assembly of strongly bonded TCNQ ionic acceptor molecules on silver surfaces},
author = {Park, Changwon and Rojas, Geoffrey A. and Jeon, Seokmin and Kelly, Simon J. and Smith, Sean C. and Sumpter, Bobby G. and Yoon, Mina and Maksymovych, Petro},
abstractNote = {The energy scales of interactions that control molecular adsorption and assembly on surfaces can vary by several orders of magnitude, yet the importance of each contributing interaction is not apparent a priori. Tetracyanoquinodimethane (TCNQ) is an archetypal electron acceptor molecule and it is a key component of organic metals. On metal surfaces, this molecule also acts as an electron acceptor, producing negatively charged adsorbates. It is therefore rather intriguing to observe attractive molecular interactions in this system that were reported previously for copper and silver surfaces. In this paper, our experiments compared TCNQ adsorption on noble metal surfaces of Ag(100) and Ag(111). In both cases we found net attractive interactions down to the lowest coverage. However, the morphology of the assemblies was strikingly different, with two-dimensional islands on Ag(100) and one-dimensional chains on Ag(111) surfaces. This observation suggests that the registry effect governed by the molecular interaction with the underlying lattice potential is critical in determining the dimensionality of the molecular assembly. Using first-principles density functional calculations with a van der Waals correction scheme, we revealed that the strengths of major interactions (i.e., lattice potential corrugation, intermolecular attraction, and charge-transfer-induced repulsion) are all similar in energy. The van der Waals interactions, in particular, almost double the strength of attractive interactions, making the intermolecular potential comparable in strength to the diffusion potential and promoting self-assembly. However, it is the anisotropy of local intermolecular interactions that is primarily responsible for the difference in the topology of the molecular islands on Ag(100) and Ag(111) surfaces. Finally, we anticipate that the intermolecular potential will become more attractive and dominant over the diffusion potential with increasing molecular size, providing new design strategies for the structure and charge transfer within molecular layers.},
doi = {10.1103/PhysRevB.90.125432},
journal = {Physical Review. B, Condensed Matter and Materials Physics},
issn = {1098-0121},
number = 12,
volume = 90,
place = {United States},
year = {2014},
month = {9}
}