TY - JOUR
T1 - Rubrene Versus Fluorine-Functionalized Rubrene Molecules on a Metal Surface
T2 - Self-Assembly, Electronic Structure, and Energy Alignment of a Monolayer on Ag(100)
AU - Viereck, Jonathan
AU - Rangan, Sylvie
AU - Häberle, Patricio
AU - Galoppini, Elena
AU - Douglas, Christopher J.
AU - Bartynski, Robert Allen
N1 - Publisher Copyright:
© 2019 American Chemical Society.
PY - 2019/6/13
Y1 - 2019/6/13
N2 - The geometric and electronic structures of a monolayer of rubrene and of a fluorinated rubrene derivative (FM-rubrene), adsorbed on a Ag(100) surface, were determined using scanning tunneling microscopy (STM), ultraviolet photoemission spectroscopy (UPS), and inverse photoemission spectroscopy (IPS) to study the influence of fluorine-functionalization on self-assembly, molecular energy levels, and energy-level alignment. STM images at room temperature reveal that the molecules form different molecular assemblies at the monolayer coverage and have the tetracene backbones nearly parallel to the surface, with strongly splayed phenyls. While the assemblies are highly ordered, the molecular orientation and intermolecular spacings differ from those of the respective molecular crystals and thus do not act as templates for the epitaxial growth of ordered multilayer molecular films. UPS and IPS measurements indicate that the frontier orbitals of an adsorbed FM-rubrene molecular layer are shifted downward with respect to the Ag(100) Fermi level by 0.2 eV as compared to those of a rubrene monolayer. Moreover, the intrinsic molecular dipole of FM-rubrene contained in the first layer leads to an interface dipole of 0.2 eV, further shifting added molecular layers to higher energies. Comparison of the adsorption of rubrene to that of FM-rubrene on Ag(100) provides valuable insights into the nature of the molecule surface and intermolecular interactions that drive self-assembly and energy-level alignment, as well as their effects on the potential growth of ordered molecular multilayers.
AB - The geometric and electronic structures of a monolayer of rubrene and of a fluorinated rubrene derivative (FM-rubrene), adsorbed on a Ag(100) surface, were determined using scanning tunneling microscopy (STM), ultraviolet photoemission spectroscopy (UPS), and inverse photoemission spectroscopy (IPS) to study the influence of fluorine-functionalization on self-assembly, molecular energy levels, and energy-level alignment. STM images at room temperature reveal that the molecules form different molecular assemblies at the monolayer coverage and have the tetracene backbones nearly parallel to the surface, with strongly splayed phenyls. While the assemblies are highly ordered, the molecular orientation and intermolecular spacings differ from those of the respective molecular crystals and thus do not act as templates for the epitaxial growth of ordered multilayer molecular films. UPS and IPS measurements indicate that the frontier orbitals of an adsorbed FM-rubrene molecular layer are shifted downward with respect to the Ag(100) Fermi level by 0.2 eV as compared to those of a rubrene monolayer. Moreover, the intrinsic molecular dipole of FM-rubrene contained in the first layer leads to an interface dipole of 0.2 eV, further shifting added molecular layers to higher energies. Comparison of the adsorption of rubrene to that of FM-rubrene on Ag(100) provides valuable insights into the nature of the molecule surface and intermolecular interactions that drive self-assembly and energy-level alignment, as well as their effects on the potential growth of ordered molecular multilayers.
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U2 - 10.1021/acs.jpcc.9b01659
DO - 10.1021/acs.jpcc.9b01659
M3 - Article
AN - SCOPUS:85067012116
SN - 1932-7447
VL - 123
SP - 14382
EP - 14390
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 23
ER -