Applied Surface Science 258 (2012) 5100–5104 Contents lists available at SciVerse ScienceDirect Applied Surface Science jou rn al h om epa g e: www.elsevier.com/locate/apsusc Substrate temperature influence on W/WCN x bilayers grown by pulsed vacuum arc discharge R. Ospina, D. Escobar, E. Restrepo-Parra ∗ , P.J. Arango, J.F. Jurado Universidad Nacional de Colombia Sede Manizales, Km. 9 vía al Magdalena, Manizales, Colombia a r t i c l e i n f o Article history: Received 6 November 2011 Received in revised form 21 January 2012 Accepted 24 January 2012 Available online 2 February 2012 Keywords: Tungsten EDS XRD Structure Raman Morphology a b s t r a c t W/WCN x coatings were produced by using a repetitive pulsed vacuum arc discharge on stainless-steel 304 substrates, varying the substrate temperature from room temperature to 200 ◦ C. Energy dispersive spectroscopy (EDS) was used for determining W, C and N concentrations dependence on the substrate temperature. A competition between C and N can be observed. Atomic force microscopy was employed for obtaining the thickness and grain size that present similar tendencies as a function of the temper- ature. X-ray diffraction characterization showed phases of W and -WCN (hexagonal). Raman spectra for all substrate temperatures were obtained, presenting two peaks corresponding to D (disorder) and G (graphite) bands in the region of 1100–1700 cm -1 due to the amorphous carbon. As an important conclu- sion, it was stated that substrate temperature has strong influence on the structure, chemical composition and morphology of W/WCN x bilayers, caused by the competition between carbon and nitrogen. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Tungsten coatings are widely used in the microelectronics industry, and the incorporation of carbon [1] and nitrogen [2] in tungsten coatings has been studied as diffusion barriers in surface modification processes [3] and many other applications. Since there appears to be a gap in the knowledge about coatings between tung- sten and tungsten carbide and nitrides, it seems reasonable trying to understand effects of a non-metallic element when it is intersti- tially incorporated in a tungsten matrix. Pauleau and Gouy-Pailler [4] concluded that the increase in coatings hardness with tungsten and small amounts of carbon was due to the isotropic dilatation of the -W structure. More recently, Quesnel et al. [5] developed W layers containing small amounts of carbon to be used in W/WC multilayers as erosion resistant coatings. Regarding to WCN x , it has been produced not only by chemical vapor deposition techniques [6–8] but also by physical vapor deposition [9–11]. The structural characterization of WCN x coatings has been normally carried out by means of X-ray diffraction (XRD) [6,12], Auger spectroscopy [13,14] and X-photoelectron spectroscopy (XPS) techniques [15,16]; on the other hand, Raman spectroscopy is a suitable tool for characteriz- ing carbon based materials. Different Raman modes for diamond, graphite and amorphous carbon have been studied by several groups [17–19]. Moreover, Raman analysis can complement results ∗ Corresponding author. Tel.: +57 6 8879495; fax: +57 6 8879495. E-mail address: erestrepopa@unal.edu.co (E. Restrepo-Parra). obtained by other techniques such as XRD and XPS, because it allows identifying D (disorder) and G (Graphite) bands. In the liter- ature, no many reports about Raman studies of WCN x coatings can be found. One work was presented by Lee et al. [20] who studied the gas-phase decomposition pathways of the tungsten dimethyl- hydrazido complexes as precursors for single source deposition of W/WNC x . Nevertheless, a depth analysis of the coating is not carried out. In this study, Raman spectroscopy in combination with elec- tron dispersive spectroscopy (EDS) and X-ray diffraction have been employed for obtaining structural information of the carbon frac- tion in the WCN x coatings produced by the pulsed vacuum arc technique. 2. Experimental set up The W and WCN x layers were deposited by using a repeti- tive pulsed vacuum arc discharge in a reaction chamber made of stainless steel. In this chamber there are two-faced electrodes, the cathode with targets of W (6N) and WC (6N) for the W and WCN x layers respectively, and the anode which contains substrates of stainless-steel 304. Coatings were produced at 4 pulses. Substrates were polished and deeply cleaned with an ultrasonic cube. A high- power source designed to generate pulses with different active and passive times was used in order to produce the discharge between electrodes. By means of this power supply it was possible to carry out variations of the inter-electrode voltage from 0 to 280 V rms (root medium square voltage), with 100 A as maximum current of 0169-4332/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2012.01.137