Characterization of as grown and nitrogen incorporated tetrahedral amorphous carbon films deposited by pulsed unfiltered cathodic vacuum arc process O.S. Panwar a, * , B. Deb b , B.S. Satyanarayana c , Mohd. Alim Khan a , R. Bhattacharyya a , A.K. Pal b a Plasma Processed Materials Group, National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi 110012, India b Department of Materials Science, Indian Association for the Cultivation of Science, Kolkata 700 032, India c Rodel Nitta Company, 172, Ikezawa-cho, Yamato Koriyama, Nara-ken 639 1032, Japan Received 29 July 2003; received in revised form 22 June 2004; accepted 25 June 2004 Available online 11 September 2004 Abstract Reported is a study of the as grown and nitrogen incorporated tetrahedral amorphous carbon (ta-C) films deposited by a pulsed unfiltered cathodic vacuum arc process using Raman scattering, photoluminescence (PL) and Fourier transform infrared (FTIR) spectroscopy. The influence of the substrate bias in as grown ta-C films and the effect of the nitrogen content in nitrogen incorporated ta-C films under a fixed bias condition were studied. The Raman spectroscopic study showed that, in the present study, the as grown ta-C films deposited at 40 V substrate bias possibly have the highest sp 3 bonded carbon concentration, as observed by the large shift in the G peak to ~1596 cm 1 . In the case of the nitrogen incorporated ta-C films, the G peak exhibited a shift towards lower wave number with increasing nitrogen content, suggesting an increase in disorder. The PL spectra indicated a strong peak ~2.21 eV arising due to extended defects like dislocations followed by a small one ~1.92 eV which could be identified as a zero phonon line (ZPL) doublet. Another peak at ~2.63 eV could be attributed to TR12 center. PL peak at ~2.21 eV showed an inflexion in ta-C films deposited at 40 V substrate bias. An increase in intensity of the PL peak at ~2.17 eV and its full width at half maximum (FWHM) value was also observed due to the increase in nitrogen content in the films. The FTIR spectra showed the characteristic peaks at 2958, 2366, 2350, 1610, 1512, 1047 and 710 cm 1 in as grown and nitrogen incorporated ta-C films. D 2004 Elsevier B.V. All rights reserved. Keywords: Raman; PL; FTIR; ta-C; Unfiltered cathodic vacuum arc; Deposition process 1. Introduction Amorphous carbon films having a high sp 3 bonded carbon content, referred as tetrahedral amorphous carbon (ta-C), continue to draw considerable interest, due to their unique mechanical, electronic, structural and morphological proper- ties [1–5]. The tribological application of the ta-C films as protective coatings over magnetic hard disks and machine tools is well established. Other potential areas of applications include, MEMS, biocompatible coatings, electron emitting cold cathodes and possible electronic and optoelectronic devices [3–7]. These ta-C films were grown by using a wide variety of processes including filtered cathodic vacuum arc (FCVA)—direct and pulsed source, pulsed laser ablation, mass selected ion beam deposition and electron cyclotron wave resonance (ECWR). The above processes being highly energetic, the controlled variation of the of ion energy led to materials with widely varying properties. Among the successful methods for the preparation of ta- C films, the FCVA technique was particularly useful for industrial applications because it provided a highly ionized plasma of energetic carbon ions, from which dense films could be grown at reasonable deposition rates [8]. However, one of the main limitations of the cathodic vacuum arc process was the presence of macroparticles. The macro- particles were generated due to the extreme conditions in the cathode arc spot, leading to macroscopic fragments of the 0040-6090/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.tsf.2004.06.164 * Corresponding author. E-mail address: ospanwar@mail.nplindia.ernet.in (O.S. Panwar). Thin Solid Films 472 (2005) 180 – 188 www.elsevier.com/locate/tsf