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Title: Molecular Self-Assembly in a Poorly Screened Environment: F 4TCNQ on Graphene/BN

Here we report a scanning tunneling microscopy and noncontact atomic force microscopy study of close-packed 2D islands of tetrafluoro-tetracyanoquinodimethane (F 4TCNQ) molecules at the surface of a graphene layer supported by boron nitride. While F 4TCNQ molecules are known to form cohesive 3D solids, the intermolecular interactions that are attractive for F 4TCNQ in 3D are repulsive in 2D. Our experimental observation of cohesive molecular behavior for F 4TCNQ 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.
 [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
Published Article
Journal Name:
ACS Nano
Additional Journal Information:
Journal Volume: 9; Journal Issue: 12; Journal ID: ISSN 1936-0851
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
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:
Alternate Identifier(s):
OSTI ID: 1257350; OSTI ID: 1378599