Journal of Colloid and Interface Science 313 (2007) 353–358 www.elsevier.com/locate/jcis Growth of highly oriented crystalline polyaniline films by self-organization D.S. Sutar a,∗ , N. Padma a , D.K. Aswal a , S.K. Deshpande b , S.K. Gupta a , J.V. Yakhmi a a Technical Physics & Prototype Engineering Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India b UGC-DAE Consortium for Scientific Research, Mumbai Centre, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India Received 12 February 2007; accepted 18 April 2007 Available online 27 April 2007 Abstract Silicon substrates with (100) orientation were modified with amino-silane self-assembled monolayer (SAM) to provide amino (NH 2 ) moieties at the substrate surface. Self-organization of polyaniline during chemical polymerization, on this modified surface, leads to the growth of highly oriented films at the substrate–polymer interface. The morphology studied using scanning electron microscopy and atomic force microscopy revealed the formation of polymer film with well faceted pyramidal crystallites. XPS and FTIR spectroscopy were used to analyze the chemical structure of the film. X-ray diffraction measurements show the crystalline nature of the polyaniline, whose lattice parameters are in agreement with the reported values. This study underlines the importance of a SAM in deciding the structure and morphology of the deposited polymer.  2007 Elsevier Inc. All rights reserved. Keywords: Polyaniline; Self-assembly; SAM; Thin films; Morphology; Structure; Crystallinity 1. Introduction The conjugated polymers are being investigated as a candi- date for organic/molecular electronics due to their unique com- bination of properties that make them an attractive alternative or a complement to the materials currently used in microelectron- ics [1,2]. However, the charge carrier mobility of conjugated polymers is generally not high enough, owing to the poor inter- grain boundaries existing between the microcrystalline domains [3–5]. Therefore, an important current pursuit of many inves- tigators has been to improve the crystallinity as well as mor- phology of conjugated conducting polymers [6,7]. One of the ways this can be achieved is to modify the surface proper- ties of the substrate on which the polymer is deposited and there has been a fair amount of progress in this direction using self-assembled monolayer (SAM) interfaces [6–11]. The three widely studied conjugated conducting polymers are polypyr- role, polythiophene and polyaniline. Polyaniline is interesting because one can carry out non-redox doping in it, uniquely, us- ing its acid–base chemistry. * Corresponding author. E-mail address: dssutar23@gmail.com (D.S. Sutar). The properties of a substrate surface are known to control the polymerization, deposition, and adhesion of conducting poly- mers [8,9]. Self-assembled monolayers can be used to mod- ify the surface by: (i) changing surface energy, rendering it hydrophobic or hydrophilic; and/or (ii) providing nucleation sites for covalent grafting of the polymer chains. In earlier reports in literature, the growing direction of the electrode- posited polypyrrole and polyaniline was controlled by using a SAM with a typical hydrophobic surface [10], and a surface of polycrystalline gold modified using self-assembled alkanethiol monolayers, was used to covalently couple o-phenylenediamine molecules for in situ chemical deposition of polyaniline and its derivatives [11]. Electroless surface polymerization of polyani- line films on aniline-primed surfaces of silicon and ITO sub- strates has been reported by Wu et al. [12,13]. They obtained dense, smooth and strongly adherent as well as ordered polyani- line films. In this case the pendant aniline functionality was used as the initiation site for polymerization and as the covalent anchor for the growth of polyaniline chains on the surface. Also, the improved transistor performance observed in case of conju- gated polymers deposited on SAM-modified surface is gener- ally attributed to better crystallinity at the polymer–substrate interface [7,14–17]. This has been indirectly shown in a study using X-ray rocking technique where the initial few layers at 0021-9797/$ – see front matter  2007 Elsevier Inc. All rights reserved. doi:10.1016/j.jcis.2007.04.051