Large-scale Solution Processable Graphene-based Thin Film Devices
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Large-scale Solution Processable Graphene-based Thin Film Devices Markus Pesonen1, Himadri S. Majumdar1, Jussi Kauppila2,3, Jukka Lukkari2 and Ronald Österbacka1 1
Center for Functional Materials, Physics, Department of Natural Sciences, Åbo Akademi University, Porthaninkatu 3, 20500 Turku, Finland 2 Department of Chemistry, University of Turku, Vatselankatu 2, 20014 Turku, Finland 3 Graduate School of Materials Research ABSTRACT The purpose of this work is to fabricate large-scale solution processable graphene-based films from graphene oxide (GO) solution and to characterize the transport properties of these films. The graphene like film is produced by annealing of the GO film to form reduced graphene oxide (rGO) thin films. The conductive rGO thin films are useable as spacer layers in spin valves and as organic electrodes. Atomic Force Microscope (AFM) characterizations on the film thickness and morphology have been carried out and simple electrical transport studies performed on spin coated rGO thin films. We have fabricated rGO thin films ranging from few to tens of nanometers in thickness with conductivities in the order of 1-100 S/m. We also show that the morphology of the films play an important role in facilitating higher conductivities for rGO thin films. INTRODUCTION The discovery of graphene has revolutionized our perception of electronics for the future. We have started looking beyond silicon and germanium towards carbon-based, green, electronics. Graphene is usually obtained from highly oriented pyrolytic graphite (HOPG) by mechanical exfoliation. Exfoliated graphene show remarkably high electron mobility at room temperature, in excess of 15,000 cm2V−1s−1. [1] The mobility is nearly independent of temperature between 10 K and 100 K, [2] which implies that the dominant scattering mechanism is defect scattering. Scattering by the acoustic phonons further reduces room temperature mobility to 4,000 cm2V−1s−1 at a carrier density of 1012 cm−2 [3]. Graphene films exhibit electric-field-dependent transport which, along with the extraordinary carrier mobility, makes them attractive as the channel material for high-frequency field effect transistors [4]. Graphene is also a promising material for spin-transport owing to the low intrinsic spin orbit interaction, as well as the low hyperfine interaction of the electron spins with the carbon nuclei [5, 6]. In spite of these extraordinary electronic properties there is a drawback to the exfoliation method for obtaining graphene. The size of the exfoliated sheets is not big – millimeters at best. This puts a serious drawback on one of the largest potential use of doing electronics with graphene – possibility of doing large-area, printable electronics. This prompted the research and development of wet chemical route for fabricating graphene. It is to be noted that large-area graphene films have been successfully fabricated and reported using chemical vapor-deposition (CVD) method [7, 8, 9] and vacuum filtration (VF) method [10]. The CVD method, however, is
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