Effect of nickel incorporation on the optical properties of diamond-like carbon (DLC) matrix B. Pandey n , S. Hussain Department of Applied Physics, Indian School of Mines, Dhanbad 826004, Jharkhand, India article info Article history: Received 25 May 2010 Received in revised form 29 March 2011 Accepted 3 June 2011 Available online 14 July 2011 Keywords: A. Thin films B. Chemical synthesis C. Electron microscopy C. Raman spectroscopy D. Optical properties abstract The present study investigates the optical behavior of composite nanostructured DLC based films and functional coatings. Diamond-like carbon (DLC) thin films were synthesized by electrodeposition method onto SnO 2 -coated glass substrates using an electrolyte of a mixture of acetic acid and water. Nanoparticles of nickel were then introduced into the DLC matrix. Morphology of the metal incorporated thin films and distribution of nanoparticles were studied by SEM; continuous homo- geneous distribution of the particles was observed. Raman spectroscopy showed additional peaks in addition to the peaks due to DLC matrix. FTIR spectra revealed new peaks in the lower wave number region due to metal inclusion. UV–vis transmittance studies were performed to calculate the band gap of the samples. The estimated band gap from the Tauc relation was found to vary from 2.63 eV for the virgin DLC to 1.48 eV for the metal incorporated DLC. & 2011 Elsevier Ltd. All rights reserved. 1. Introduction Since the discovery of diamond-like carbon (DLC) thin films by Aisenberg and Chabot in the early 1970s, thin films have been a subject of expanding technological interest due to their attractive properties such as low friction coefficient, high hardness, thermal conductivity, optical transparency, non-wettability, chemical inertness, high wear resistance, high corrosion resistance and biocompatibility [1–7]. DLC films are composed of graphitic clusters joined together by sp 2 (p) and sp 3 (s) bondings, resulting in an extended carbon network. The relative ratio of the sp 2 /sp 3 bonds present in the network governs various features of DLC. However a variety of techniques for the synthesis of DLC gen- erally adopted by researchers, namely CVD and PVD, have been questioned for their scalability and cost effectiveness [8]. More- over the composite films deposited by these methods are not evenly dispersed. A quest for low-cost and scalable deposition technique is still under the way, which has led to the synthesis of the DLC films by electrodepostion method [9–11]. In the past some workers have successfully demonstrated the deposition of DLC films from the electrolysis of various organic liquids [12–14]. DLC films have optical transparency from ultraviolet to infrared with a large tunable band gap and have varied amount of sp 2 /sp 3 bond ratio. They can act as a suitable host matrix for inclusion of metals in nanocrystalline form and the above properties can be manipulated and suitably tailored [15–18]. Metal inclusion into the system enhances adhesion of the thin film layer to the substrate and reduces peeling off [19–22]. Metal in nanocrystalline form exhibits a wide range of properties different from the bulk [23–28]. The DLC matrix helps encapsu- late the properties of the nanoparticles and thus retain their individuality [4]. However, maneuvering metal incorporation into the DLC matrix is still a matter of great challenge. Though a few groups have reported the successful incorporation of metals into the DLC matrix by chemical and physical vapor deposition techniques [3–5,29–33], still there is a difficulty in homogeneous and uniform distribution of metal particles in the DLC matrix. In this regard electrodeposition method proves to be beneficial as it not only allows uniform distribution but also has the ability to deposit the material over irregular surfaces. Earlier works on the metal impregnation by electrochemical route have reported [34–35] noble metals dispersed into the DLC matrix. Various groups have already incorporated/doped nickel in DLC matrices by a variety of methods. Results show the incorporation of nickel contributing to the effective decrease in the residual stress and an increase in the bonding strength of the Ni-doped DLC film, which result in significantly increased wear resistance [36]. The results also indicate that the corrosion resistance of the Ni-DLC films decreases with the increased Ni content in the films [37]. Compared with pure carbon films, nickel incorporation greatly enhances graphitization of carbon films and reduces surface tension [38]. Here we report for the first time on a magnetic metal nickel being impregnated into DLC by chemical route. Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jpcs Journal of Physics and Chemistry of Solids 0022-3697/$ - see front matter & 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.jpcs.2011.06.003 n Corresponding author. Tel.: þ91 3262296620; fax: þ91 3262296563. E-mail address: pandey.beauty@yahoo.com (B. Pandey). Journal of Physics and Chemistry of Solids 72 (2011) 1111–1116