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Title: Molecular Self-Assembly in a Poorly Screened Environment: F4TCNQ on Graphene/BN

Here we report a scanning tunneling microscopy and noncontact atomic force microscopy study of close-packed 2D islands of tetrafluoro-tetracyanoquinodimethane (F4TCNQ) molecules at the surface of a graphene layer supported by boron nitride. While F4TCNQ molecules are known to form cohesive 3D solids, the intermolecular interactions that are attractive for F4TCNQ in 3D are repulsive in 2D. Our experimental observation of cohesive molecular behavior for F4TCNQ on graphene is thus unexpected. This self-assembly behavior can be explained by a novel solid formation mechanism that occurs when charged molecules are placed in a poorly screened environment. As negatively charged molecules coalesce, the local work function increases, causing electrons to flow into the coalescing molecular island and increase its cohesive binding energy.
Authors:
 [1] ;  [1] ;  [2] ;  [2] ;  [2] ;  [3] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [4] ;  [4] ;  [3] ;  [2] ;  [5] ;  [2] ;  [3]
  1. Univ. of California, Berkeley, CA (United States)
  2. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  3. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Korea Institute for Advanced Study, Seoul (Korea)
  4. National Institute for Materials Science,Tsukuba (Japan)
  5. Univ. of California, Berkeley, CA (United States); National University of Singapore (Singapore)
Publication Date:
Grant/Contract Number:
AC02-05CH11231; J3026-N16; R-144-000-295-281; P2ELP2-151852; 32 CFR 168a; DMR-1206512
Type:
Published Article
Journal Name:
ACS Nano
Additional Journal Information:
Journal Volume: 9; Journal Issue: 12; Journal ID: ISSN 1936-0851
Publisher:
American Chemical Society (ACS)
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
47 OTHER INSTRUMENTATION; molecular self-assembly; graphene; hexagonal boron nitride (BN); scanning tunneling microscopy (STM); noncontact atomic force microscopy (nc-AFM); density functional theory (DFT); 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 36 MATERIALS SCIENCE
OSTI Identifier:
1224916
Alternate Identifier(s):
OSTI ID: 1257350; OSTI ID: 1378599