pubs.acs.org/cm Published on Web 01/13/2011 r 2011 American Chemical Society 970 Chem. Mater. 2011, 23, 970–975 DOI:10.1021/cm1025975 Simple Formation of C 60 and C 60 -Ferrocene Conjugated Monolayers Anchored onto Silicon Oxide with Five Carboxylic Acids and Their Transistor Applications Yoshimitsu Itoh,* ,†,z,^ Bumjung Kim, † Raluca I. Gearba, ‡ Noah J. Tremblay, † Ron Pindak, # Yutaka Matsuo, §, z Eiichi Nakamura, §, z and Colin Nuckolls † † Deparment of Chemistry and The Center for Electron Transport in Molecular Nanostructures, Columbia University, New York, New York 10027, United States, ‡ Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, United States, # National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York 11973, United States, § Nakamura Functional Carbon Cluster Project, ERATO, Japan Science and Technology Agency, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan, and z Department of Chemistry, The Univeristy of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan. ^ Current address of Y. I. Department of Chemistry and Biotechnology, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan. Received September 9, 2010. Revised Manuscript Received December 11, 2010 C 60 and C 60 -ferrocene conjugated molecule bearing five carboxylic acids successfully anchor onto a silicon oxide surface as a monolayer through a simple method of simply dipping an amino-terminated surface into the solution of the C 60 derivatives. The monolayer structure was characterized by UV-vis spectroscopy, X-ray reflectivity, X-ray photoelectron spectroscopy, and IR spectroscopy to reveal that the molecules are standing presenting its C 60 spherical face at the surface. The electronic effect of the C 60 monolayer and the ferrocene-functionalized C 60 monolayer in OFET devices was investigated. When an n-type OFET was fabricated on the ferrocene functionalized monolayer, we see an enhancement in the mobility. When a p-type OFET was made the ferrocene-functionalized C 60 monolayer showed a lowering of the carrier mobility. Introduction In this study, we investigate self-assembled monolayers (SAMs) of anisotropically functionalized C 60 molecules, and we explore the feasibility of these SAMs as electrically active materials in field-effect transistors (FETs). C 60 , also known as buckminsterfullerene, 1 is an attractive material for electronic applications, such as photovoltaics and FETs 2,3 as suggested by its high electron mobilities. 4 Of particular interests are the SAMs 5 of C 60 showing unique properties and potential for advanced electronic applications. 6 There have been many studies of a monolayer of C 60 derivatives on gold, ITO, or other substrates. 7 However, compared to the monolayer on gold, there are only a few reports for the formation of fullerene monolayers on silicon oxide surfaces 8 that are important for electronic device applications especially for organic FETs. Moreover, all of these prior studies involve covalent functionalization on silicon oxide surfaces. 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