ABSTRACT:We fabricated polymer-laminated, transparent, all-carbon-nanotube field-effect transistors (CNTFETs), making use of the flexible yet robust nature of single-walled carbon nanotubes (SWNTs). All components of the FET (active channel, electrodes, dielectric layer, and substrate) consist of carbon-based materials. The use of a plastic substrate that is considerably thinner than those used in other flexible CNT-FETs allowed our devices to be highly deformable without degradation of electrical properties. Using this approach, flexible, transparent CNT-FET devices able to withstand a 1 mm bending radius were realized. a) Author to whom correspondence should be addressed. E-mail: maruyama@photon.t.u-tokyo.ac.jp 2 Field-effect transistors (FETs) based on single-walled carbon nanotubes (SWNTs), [1][2][3][4][5][18][19][20] or ITO 6,7,[13][14][15][16] as the electrode material. The use of Au diminishes the optical transparency, whereas brittle ITO limits the mechanical flexibility of the device. 21,22 To simultaneously improve upon both of these aspects, carbon nanotube FETs (CNT-FETs) employing SWNTs 8 or graphene [9][10][11][12] for all electrodes (source, drain, and gate) have recently been reported.These metal-free devices can realize both optical transparency and mechanical robustness, but flexibility is typically sacrificed by fabricating the devices on thick plastic substrates. As suggested by Hur et al.
2and Cao et al.,8 combining SWNTs with a thin, flexible material could lead to devices that are able to be wrinkled like paper.
23In this study, we demonstrate the realization of all-CNT-FETs in which all channels and electrodes (source, drain, and gate) are composed of SWNTs, and the substrate and dielectric layer are made of poly(vinyl alcohol) (PVA). The devices are fabricated using a simple transfer process followed by lamination using polymer sheets, and exhibit extreme flexibility and robustness to mechanical deformation.A schematic illustrating the layered structure of the all-CNT-FET is shown in Fig. 1(a). To fabricate the device, a Si wafer was cut into 2 pieces, and on one of these pieces a 1 square inch active layer (S/D electrodes and channel) was prepared. On the other piece, a 0.5 × 1 inch global gate electrode was prepared. The larger substrate was patterned using standard photolithography processes (exposure and development). After patterning, Co catalyst (thickness: 0.5 nm) was deposited onto both the photolithography-defined and non-patterned substrates using a thermal evaporator. The patterned substrate was then washed by dipping into acetone to remove residual resist (lift-off), rinsed with isopropyl alcohol (IPA), and dried using a nitrogen gun. SWNTs were then synthesized on both substrates using the alcohol catalytic chemical vapor deposition (ACCVD) 3 method.
24Details regarding the synthesis procedure have been described elsewhere. [25][26][27] This approach enables us to synthesize both the channels and S/D electrodes in a single CVD step.
28The device substrate and dielectric lay...
