Noncontact Atomic Force Microscopy - Yale School of Engineering ...

Molecular Structures of Organic Single Crystals Investigated by
Frequency Modulation Atomic Force Microscopes
Taketoshi Minato 1 , Hiroto Aoki 2 , Thorsten Wagner 3 2, 4
, and Kingo Itaya
129
P.II-01
1
Institute for International Advanced Interdisciplinary Research (IIAIR), Tohoku Univ., 6-6-07 Aoba,
Aramaki, Aoba-ku, Sendai, Miyagi 980-8579, Japan
2
Department of Applied Chemistry, Tohoku Univ., 6-6-07 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-
8579, Japan
3
University at Duisburg-Essen, Fachbereich Physics, Lotharstr. 1-21, 47057 Duisburg, Germany
4
World Premier International Research Center (WPI), Tohoku Univ., 6-6-07 Aoba, Aramaki, Aoba-ku,
Sen-dai, Miyagi 980-8579, Japan
Recently, single crystals of organic semiconductors such as rubrene [1],
pentacene [2] and PTCDA [3] are attracting great interest as materials to be used for
organic field effect transistors (OFETs). It is important to characterize geometric and
electronic structures of organic layers in molecular levels in order to achieve higher
carrier mobility. Here, we describe applications of Frequency Modulation Atomic Force
Microscopy (FM-AFM) for single crystal to investigate the molecular structure [4, 5].
First, we measured FM-AFM images on
prepared pentance single crystals in UHV. The
obtained molecular resolved FM-AFM images
showed very wide terrace (2 – 3 um) and high
crystallity of prepared single crystal without
molecular defects [2]. Also, we have recently
achieved molecular resolution on a rubrene single
crystal in UHV [5]. Fig. 1 shows a FM-AFM
image in 5.0 nm × 5.0 nm. This also showed high
crystallity of prepared single crystal without
molecular defects as same as pentacene single
crystals. Such results strongly suggest that the
prepared organic single crytals are applicable to
OFETs.
Figure 1 A FM-AFM image
(5.0 nm × 5.0 nm) of rubrene
single crystal. Tsample = 298 K.
References
[1] R. W. I. de Boer, M. E. Gershenson, A. F.
Morpurgo, V. Podzorov, Phys. Status Solidi A, 201, 1302 (2004).
[2] V. Y. Butko, X. Chi, D. V. Lang, A. P. Ramirez, Appl. Phys. Lett. 83, 4773 (2003).
[3] T. Wagner, A. Bannani, C. Bobisch, H. Karacuban, M. Stohr, M. Gabriel, R. Moller,
Org. Elect., 5, 35 (2004).
[4] K. Sato, T. Sawaguchi, M. Sakata, and K. Itaya, Langmuir, 23, 12788 (2007).
[5] T. Minato, H. Aoki, T. Wagner, H. Fukidome and K. Itaya, J. Am. Chem. Soc.,
submitted (2009).