Characterization of nanocrystalline gold/DLC composite films synthesized by plasma CVD technique R. Paul, S. Hussain, A.K. Pal * Department of Instrumentation Science, USIC Building, Jadavpur University, Kolkata 700032, India 1. Introduction Metal nanoparticles in the nanometer-size range have been the subject of much scientific research due to their characteristic properties that are distinctly different from their bulk counter parts [1–10]. Particular interest has been focused on the noble metal nanoparticles because they are technologically important in many fields. Size-dependent electrical, optical and catalytic properties, biological assays, and surface-enhanced Raman scat- tering (SERS) were the main subject of these studies [9,10]. These systems exhibited a large third-order nonlinear susceptibility and fast time response near surface plasmon resonance frequency [11,12]. Recently, several researchers [5–7,13–16] have reported their studies on optical properties of gold or silver nanoparticles embedded in dielectric matrix. The choice of the dielectric matrix was limited mainly to SiO 2 and ZnO [13,14]. Isolated gold nanoparticles have also demonstrated high catalytic activity for both oxidation and reduction reactions [1,8,15,17,18]. The synthesis of nanoparticulate gold films encapsuled in different matrix has been reported by a number of groups [1– 8,18,19] using numerous techniques, which includes precipitation, physical vapour deposition (PVD), chemical vapour deposition (CVD), and organic encapsulation. The main hurdle to the widespread application of metal nanoparticles is their agglomera- tion due to high surface energy [18,19]. Metal doping in diamond- like carbon (DLC) films prepared by chemical/physical vapour deposition techniques had been the issue for obtaining a new class of materials [20–22] for tribological applications. But the difficulty of dispersing the metal in nanocrystalline form homogeneously in the DLC matrix was found to be a difficult proposition. In recent times, incorporation of silver nanoparticles in DLC matrix by electrodeposition technique and related surface plasmon reso- nance effect was reported by Hussain et al. [21] But, reports on incorporation of Ib metal nanoparticles by CVD technique seemed to be still a challenge to the scientists. In this communication, we present our studies on composite material consisting of nanocrystalline gold particles having different grain sizes as well as inter-grain distances embedded in diamond-like carbon matrix. The above composite films were prepared by capacitatively coupled plasma (CCP) chemical vapour deposition (CVD) technique. Films were characterized by measur- ing microstructural and optical properties. Raman and FTIR studies were carried out to obtain information on the bonding environ- ment in these films. 2. Experimental details Nanocrystalline gold/DLC composite films (Au–DLC) were deposited by capacitatively coupled r.f. (13.56 MHz) plasma chemical vapour deposition technique. The plasma was generated between two circular aluminium discs. The top aluminium disc was used to hold a 1.0 mm thick gold disc of same diameter and Applied Surface Science 255 (2009) 8076–8083 ARTICLE INFO Article history: Received 9 March 2009 Received in revised form 8 May 2009 Accepted 11 May 2009 Available online 15 May 2009 PACS: 78.67.n Keywords: Surface plasmon Diamond-like carbon Nanocrystalline gold ABSTRACT Composite films containing gold nanoparticles embedded in diamond-like carbon (Au–DLC) matrix were deposited on glass and Si (1 0 0) substrates by using capacitatively coupled plasma (CCP) chemical vapour deposition technique (CVD). Particle size and metal volume fraction were tailored by varying the relative amount of argon in the methane + argon gas mixture in the plasma. Optical constants of the films were evaluated. Bonding environment in these films were obtained from Raman and Fourier transformed infrared spectra (FTIR) studies. Blue-shift of the surface plasmon resonance peak in the optical absorbance spectra of the films could be associated with the reduction of the particle size while red shift was observed with the increase in volume fraction of metal particles in the DLC films. Absorption spectra recorded in the reflection mode indicated dichromatism in these films. ß 2009 Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +91 33 24146321; fax: +91 33 24146584. E-mail address: msakp2002@yahoo.co.in (A.K. Pal). Contents lists available at ScienceDirect Applied Surface Science journal homepage: www.elsevier.com/locate/apsusc 0169-4332/$ – see front matter ß 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2009.05.018