Analysis of nitrogen-doped ion-beam-deposited hydrogenated diamond-like carbon films using ERDA/RBS, TOF-ERDA and Raman spectroscopy M. Čekada a, ⁎, M. Kahn b, 1 , P. Pelicon a , Z. Siketić a, c , I. Bogdanović Radović c , W. Waldhauser b , S. Paskvale a a Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia b Joanneum Research, MATERIALS — Institute for Surface Technologies and Photonics, Leobnerstr. 94, 8712 Niklasdorf, Austria c Rudjer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia abstract article info Available online 10 September 2011 Keywords: Diamond-like carbon ERDA TOF-ERDA Raman spectroscopy Anode layer source In this work we deposited a series of hydrogenated amorphous carbon (a-C:H) films and nitrogen-doped a-C:H films on silicon substrates using an ion-beam-deposition technique called anode layer source. We used different discharge voltages, which influence the sp 2 /sp 3 carbon hybridization ratio, and we also varied the N 2 -to-C 2 H 2 flow ratios. The composition was analysed by elastic recoil detection analysis (ERDA), to determine the hydrogen content, in combination with Rutherford backscattering spectroscopy (RBS), for the heavier elements. An additional set of experiments was conducted by time-of-flight (TOF) ERDA, which gives information not only about the hydro- gen content but also about the content of other lighter elements (C, N and O) in the sample. The influence of the deposition parameters on the chemical composition and the structure of the films (studied by Raman spectros- copy) was thus evaluated. The discharge voltage did not have a measurable effect on the composition (but a de- cisive one on the structure), while the nitrogen flow variations were clearly proven in respective trends in the chemical composition and structure variations. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Diamond-like carbon (DLC) films have been studied intensively in the past few decades. However, due to their amorphous nature, their structure is difficult to evaluate. A common tool for this purpose is Raman spectroscopy; however, the results have to be interpreted with care. A good guide is the work by Casiraghi et al. [1] for the interpretation of spectra taken from hydrogenated amorphous carbon films (a-C:H). The interpretation becomes even more complicated if the a-C:H is doped with nitrogen [2–5]. In this case it is essential to evaluate the sam- ples by applying Raman spectroscopy at two different wavelengths. While Raman spectroscopy provides clues about the sp 2 configu- ration and structural disorder, i.e., amorphisation, the information about the hydrogen concentration is only indirect. Classical electron spectroscopies cannot be used for the hydrogen determination. One of the methods of choice is elastic recoil detection analysis (ERDA). It is commonly used in combination with Rutherford backscattering spectroscopy (RBS), utilising the same primary beam. Yet another op- tion is to combine ERDA with a time-of-flight (TOF) spectrometer. ERDA has been used to evaluate the hydrogen concentration in DLC films [6,7], in some cases also in combination with Raman spectroscopy [8,9]. A wide range of hydrogen concentrations has been measured, from 3 to 5 at.% for non-hydrogenated DLC [9] up to 50 at.% (see [7] and refer- ences therein). Among the many techniques for the deposition of a-C:H, the anode layer source remains a little known but promising technique [10,11]. The absence of solid targets provides an almost defect-free film surface, and its wide range of deposition parameters enables tun- ing of the film's properties. We analysed several aspects of a-C:H de- position using an anode layer source [12,13]. In previous work we found distinct relations between the Raman band parameters and the mechanical properties of a-C:H films deposited using an anode layer source [14]. There, ERDA investigations provided essential infor- mation about the hydrogen contents of the films deposited over the whole working area of the source. In this work we are expanding this knowledge by applying ERDA/RBS and TOF-ERDA investigations to evaluate the hydrogen and nitrogen concentration in nitrogen-doped a-C:H films (a-C:H:N), not discussed so far. Consequently, dual-wavelengths Raman spectroscopy is applied to evaluate the role of nitrogen in the structural evolution of these films. 2. Experimental 2.1. Film deposition The films were deposited using an ALS340L anode layer source from Vecco Instruments (Woodbury, USA) on (100) oriented boron-doped Surface & Coatings Technology 211 (2012) 72–75 ⁎ Corresponding author. Tel: +386 1 477 3796; fax: +386 1 2519 385. E-mail address: miha.cekada@ijs.si (M. Čekada). 1 Current address: Infineon Technologies Austria AG, Siemensstr. 2, 9500-Villach, Austria. 0257-8972/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.surfcoat.2011.08.057 Contents lists available at SciVerse ScienceDirect Surface & Coatings Technology journal homepage: www.elsevier.com/locate/surfcoat