Advanced AFM investigations of model molecular systems
for organic electronics
B. Grévin1*, R. Demadrille1, Y. Luo1, P. Rannou1
1
UMR5819-SPrAM (CEA-CNRS-UJF) CEA-Grenoble INAC/SPrAM/LEMOH, 17 rue des
Martyrs 38054 Grenoble cedex 9, France.
*benjamin.grevin@cea.fr
M. Linares2, R. Lazzaroni2, Ph. Leclère2
2
Service de Chimie des Matériaux Nouveaux, Université de Mons-Hainaut, Place du Parc,
20 B-7000 Mons.
Nowadays, near field microscopy techniques are essential tools for fundamental and
technological research in the field of organic and molecular electronics. A thorough knowledge of the
molecular conformation, self-organization and electronic properties on surfaces is indeed mandatory
for the optimization of electronic and optoelectronic devices with smart functionalities.
This past decade, Atomic Force Microscopy (AFM) techniques have been widely applied in
ambient conditions (amplitude modulation AFM, also called intermittent contact AFM) to characterize
the microscopic morphology of a tremendous amount of π -conjugated oligomers and polymers
deposited in thin films on conducting and insulating surfaces [1], such as dielectrics used for the gate
in OFETs. Particularly, the fibrillar organization of solution processed edge-on supramolecular stacks,
yielding high mobilities in OFETs, has been investigated and reported by many groups [1-3]. Following
these research, it is now widely agreed that these edge-on molecular assemblies are mandatory to
achieve high carrier mobilities under field effect doping. Besides, the potentiometric and electrostatic
modes of AFM have also been used for local investigations of the electronic transport properties in
thin-film based OFETs [4-5], and to probe the photo-generation of charge carriers in donor-acceptor
polymer blends [6-7]. However, despite a tremendous number of AFM studies, the exact nature of the
molecular packing within the assemblies remains often unknown, due to the limits in spatial resolution
of AFM in the amplitude modulation mode. Intermittent contact images revealed the fibrillar
organization of the stacks but with no real supramolecular resolution. Non-contact AFM (NC-AFM)
under ultra-high vacuum (UHV) in the frequency modulation mode (FM-AFM), which provides a higher
resolution [8] than intermittent contact AFM, appears henceforth as a new promising technique.
In this context, we show that NC-AFM can provide information with unprecedented resolution
on the molecular conformation within functional supra-molecular stacks self-assembled from solution.
The nature of the molecular conformations within thiophene-fluorenone oligomer self-assemblies, is
discussed in terms of topographic and spectroscopic (i.e. dissipation images) images, supported by
theoretical modeling.
In a second part, it is shown that scanning Kelvin probe microscopy (SKPM), an AFM-based
potentiometric technique, allows for an in-depth exploration of the local electrical potential at the
organic/dielectric interface in sub-μm thick organic single crystals (OSCs), opening novel perspectives
for a deeper understanding of intrinsic charge transport, interfacial and contact effects in semiconducting organic single crystals [9].
[1] Ph. Leclère et al., Materials Science and Engineering R55, 1 (2006)
[2] R.J. Kline et al., Adv. Mater. 15, 1519 (2003)
[3] B.S. Ong et al., Adv. Mater. 17, 1141 (2005)
[4] L. Bürgi, H. Sirringhaus, R. H. Friend, Appl. Phys. Lett. 80, 2913 (2002)
[5] K. P. Puntambekar, P. V. Pesavento, C. D. Frisbie, Appl. Phys. Lett. 83, 5539 (2003)
[6] A. Liscio et al., J. Am. Chem. Soc. 130, 781 (2008)
[7] V. Palermo et al., Adv. Funct. Mater. 17, 472 (2007)
[8] F.J. Giessibl Rev. Mod. Phys. 75, 949 (2003)
[9] Y. Luo et al., Adv. Mater. 19, 2267 (2007)
B. Grévin
Chargé de Recherche au CNRS
Private Address:
52 impasse des Châtaigniers
38470 Vinay - FRANCE
Professional Address:
UMR5819 SPrAM CEA-CNRS-UJF
CEA-Grenoble INAC/SPrAM/LEMOH
17 rue des Martyrs 38054 Grenoble cedex 9
FRANCE
Phone : + 33 (0)4 38 78 46 15
Fax : + 33 (0)4 38 78 51 13
E-mail: benjamin.grevin@cea.fr
Benjamin Grevin (born in 1970 in France) studied physics at the Institut National
Polytechnique de Grenoble (INPG) where he received his Engineer diploma, and also
obtained a Master Science degree in physics at the University Joseph Fourier Grenoble I. He
performed his Ph.D. at the Laboratoire de Spectrométrie Physique of University Joseph
Fourier Grenoble I under the supervision of Dr. Yves Berthier; working on NMR
investigations of cuprates superconductors. From 1998–2000 he worked on STM
investigations of manganites thin films, as a postdoctoral research fellow at the Département
de Physique de la Matière Condensée (DPMC) of University of Geneva, in the group leaded
by Prof. Ø. Fischer. Since the end of 2000, he is working within UMR5819-SPrAM (CEACNRS-UJF) as Chargé de Recherche au CNRS. His current research is focused on the use
of scanning probe microscopy techniques (STM/STS, AFM/SKPM) for local investigations of
model molecular and macromolecular pi-conjugated self-assemblies and operating organic
devices. His work has been awarded the bronze medal of CNRS (2005).