ISSN 1063-7850, Technical Physics Letters, 2015, Vol. 41, No. 1, pp. 94–97. © Pleiades Publishing, Ltd., 2015. Original Russian Text © A.V. Emelianov, K.F. Akhmadishina, A.V. Romashkin, V.K. Nevolin, I.I. Bobrinetskiy, 2015, published in Pis’ma v Zhurnal Tekhnicheskoi Fiziki, 2015, Vol. 41, No. 2, pp. 87–95. 94 Flexible transparent conducting coatings are among the main components of new electronic devices such as organic transistors, displays, solar cells, and light-emitting diodes. At present, the most widely used material for manufacturing transparent electrodes is indium–tin oxide (ITO) [1, 2]. A possible alternative to ITO is offered by coatings based on car- bon nanotubes (CNTs) and graphene [3, 4]. The main disadvantage of conducting coatings based on carbon nanomaterials is their cluster nature, which hinders the formation of a continuous film capable of ensuring nondissipative transport of free charge carriers [5]. One possible way to engage in large-scale fabrication of transparent conducting coatings is via the creation of composites consisting of carbon nanomaterials and conducting polymers [6, 7]. An alternative approach that ensures adaptation of the technology of CNT integration for the creation of electrodes is probably related to the formation of molecular transport channels in the gap between nan- otubes by means of the orientation of molecules dur- ing their interaction with CNTs even in the absence of polymer doping [8]. The present work was aimed at the development of methods for the formation of transparent conducting films based on CNTs and polymers on flexible sub- strates and the investigation of mechanisms capable of improving the transport of charge carriers in these films. We have prepared stabilized colloidal solutions of carboxylic acid functionalized single-walled carbon nanotubes (c-SWNTs) (Aldrich) and c-SWNT/polya- niline (PANI) in the emeraldine base form in dimeth- ylacetamide (DMA). The c-SWNT concentration was 1 mg/mL, and the PANI concentration was 0.01 mg/mL. These solutions were applied in 0.05 mL drops by several iterations onto the surface of polyeth- ylene naphthalate (PEN, Teijin DuPont Films) and distributed over the substrate surface by centrifuging. After application of the c-SWNT/PANI composite, the films were exposed to HCl vapor for 24 h, which led to the doping of PANI, and then the samples were dried for 10 min at 100–110°C. This application and treatment procedure was repeated to obtain more per- colated networks. Figure 1 shows atomic-force microscopy (AFM) images (Solver-P47, NT-MDT) of coatings obtained upon the application of a single layer of nanotubes and a related composite. The AFM data were used to determine the thicknesses of obtained porous films. The height of individual c-SWNTs did not exceed 1– 2 nm, which is evidence of a high dispersion of the obtained solutions (Fig. 1a). The minimum size of fibers in c-SWNT/PANI films was 2–3 nm (Fig. 1b), which indicates that PANI envelops CNTs, thus increasing their diameters on the image. Finally, 100-nm-thick palladium electrodes were deposited onto the obtained structures and the sam- ples were characterized by measuring the sheet resis- tance and optical transmittance (transparency). With increasing number of solution applications, both the resistance and transparency decreased. We have studied the effect of doping in HCL vapor on resistance R of c-SWNT/PANI films and the dependence of R on the number of sequential layer applications (Fig. 2a). It has been previously estab- lished [9] that the absolute resistance of pure CNTs nonlinearly depends on the number of applications, which can be related to the organization of three- dimensional (3D) conduction channels in the matrix of CNTs. Nevertheless, the effect of doping in all cases changes the resistance by δR ~ 41 ± 2%, which con- Features of Flexible Transparent Conducting Films Based on Polyaniline–Carbon Nanotube Composite A. V. Emelianov*, K. F. Akhmadishina, A. V. Romashkin, V. K. Nevolin, and I. I. Bobrinetskiy National Research University of Electronic Technology, Zelenograd, Moscow, 124498 Russia *e-mail: emmsowton@gmail.com Received July 8, 2014 Abstract—We propose a new concept in the formation of transparent conducting films based on single- walled carbon nanotubes (SWNTs) and polyaniline (PANI) on a flexible polyethylene naphthalate substrate. It is established that the resistance of SWNT–PANI composite films decreases to less than half as compared to pure nanotubes, while the transparency is retained. Mechanisms responsible for a change in the conduc- tivity of composite molecular systems are discussed based on differences in the transport of charge carriers in nanotubes and the polymer with allowance for their interaction. DOI: 10.1134/S106378501501023X