Molecular Self-Assembly in a Poorly Screened Environment: F4TCNQ on Graphene/BN.
We report a scanning tunneling microscopy and noncontact atomic force microscopy study of close-packed 2D islands of tetrafluorotetracyanoquinodimethane (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.
Department of Physics, University of California , Berkeley, California 94720, United States.
Hsin-Zon
HZ
Tsai
Department of Physics, University of California , Berkeley, California 94720, United States.
Arash A
AA
Omrani
Department of Physics, University of California , Berkeley, California 94720, United States.|Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
Sinisa
S
Coh
Department of Physics, University of California , Berkeley, California 94720, United States.|Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
Hyungju
H
Oh
Department of Physics, University of California , Berkeley, California 94720, United States.|Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
Sebastian
S
Wickenburg
Department of Physics, University of California , Berkeley, California 94720, United States.|Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.|Korea Institute for Advanced Study , Seoul 130-722, Korea.
Young-Woo
YW
Son
Department of Physics, University of California , Berkeley, California 94720, United States.
Dillon
D
Wong
Department of Physics, University of California , Berkeley, California 94720, United States.
Alexander
A
Riss
Department of Physics, University of California , Berkeley, California 94720, United States.
Han Sae
HS
Jung
Department of Physics, University of California , Berkeley, California 94720, United States.
Giang D
GD
Nguyen
Department of Physics, University of California , Berkeley, California 94720, United States.
Griffin F
GF
Rodgers
Department of Physics, University of California , Berkeley, California 94720, United States.
Andrew S
AS
Aikawa
National Institute for Materials Science , 1-1 Namiki, Tsukuba, 305-0044, Japan.
Takashi
T
Taniguchi
National Institute for Materials Science , 1-1 Namiki, Tsukuba, 305-0044, Japan.
Kenji
K
Watanabe
Department of Physics, University of California , Berkeley, California 94720, United States.|Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.|Kavli Energy NanoSciences Institute at the University of California, Berkeley and the Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
Alex
A
Zettl
Department of Physics, University of California , Berkeley, California 94720, United States.|Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
Steven G
SG
Louie
Department of Physics, University of California , Berkeley, California 94720, United States.|Department of Chemistry, National University of Singapore , 3 Science Drive 3, Singapore 117543, Singapore.|Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore , 6 Science Drive 2, Singapore 117546, Singapore.
Jiong
J
Lu
Department of Physics, University of California , Berkeley, California 94720, United States.|Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
Marvin L
ML
Cohen
Department of Physics, University of California , Berkeley, California 94720, United States.|Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.|Kavli Energy NanoSciences Institute at the University of California, Berkeley and the Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
Michael F
MF
Crommie
density functional theory (DFT); graphene; hexagonal boron nitride (BN); molecular self-assembly; noncontact atomic force microscopy (nc-AFM); scanning tunneling microscopy (STM)