ORIGINAL RESEARCH Study of Structural and Mechanical Properties of WN/a-Si 3 N 4 Hard Coatings Grown by Plasma Focus Ali Hussnain • Rajdeep Singh Rawat • Tan Kim Seng • Riaz Ahmad • Tousif Hussain • Paul Lee • Chen Zhong • Shen Lu • Zhang Zheng Published online: 7 December 2014 Ó Springer Science+Business Media New York 2014 Abstract WN/a-Si 3 N 4 thin films have been synthesized by utilizing the energetic ion/electron species emanated from hot, dense pinched plasma column in UNU/ICTP plasma focus operated with nitrogen gas. Structural, chemical, morphological and mechanical properties of synthesized films are studied using X-ray diffraction (XRD), X-ray photoelectron spectroscopic (XPS), field emission scanning electron microscopy (FESEM) and nano-indentation respectively. XRD spectra show WN 2 , WN, WSi 2 phases on exposed samples. XPS results con- firm W–Si–N chemical bonding in synthesized films. FE- SEM micrographs show uniform granular structure of synthesized WN/a-Si 3 N 4 thin films. Surface morphology of synthesized thin films shows that increase in focus shots strongly affects the grain size due to change in ion energy flux. Nano-indentation results show significant increase in hardness with increase in focus shots with maximum hardness of 23.5 ± 1 GPa is observed for 45 focus shots. Keywords Plasma focus  Tungsten nitride  Thin films  Nano-indentation  XRD  XPS  Morphology Introduction Plasma focus is a pulsed discharge device that utilizes self- generated magnetic field to produce a high temperature (*1–2 keV), high density (10 25 –10 26 m -3 ) and short lived (0.01–0.1 l sec) pinch plasma. The pinch plasma column is a copious source of energetic radiation such as X-rays, neutrons, relativistic electrons and highly energetic ions having energies in between 25 and 8 MeV [1–3], depend- ing upon the operating energy (from a few kJ to MJ) and type of filling gas. Various researchers have utilized ions/ electrons of plasma focus device for ion implantation [4] surface modification [5] and thin films deposition at room temperature [6–8]. The plasma focus (PF) is being employed for thin film deposition because it possesses attractive features for deposition purposes such as: (a) deposition is assisted by energetic ions and hence can be referred as energetic deposition, (b) deposition rates are high, (c) film adhesions to substrate surface is generally good, (d) deposition under different reactive background gas is allowed and (e) in situ or post deposition heating is not required for crystalline phase formation [9–12]. Thin film deposition at room temperature conditions is highly desirable as depositions at elevated temperature limit the choice of substrate material. Therefore plasma focus device is attractive for deposition on substrate materials at room temperature. A. Hussnain  R. S. Rawat  T. K. Seng  P. Lee NSSE, National Institute of Education, Nanyang Technological University, Singapore 637616, Singapore A. Hussnain Department of Physics, GC University, Lahore 54000, Pakistan R. Ahmad (&)  T. Hussain Centre for Advance Studies in Physics (CASP), GC University, Lahore 54000, Pakistan e-mail: ahriaz@gcu.edu.pk; ahriaz@gmail.com C. Zhong School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore S. Lu  Z. Zheng Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 3 Research Link, Singapore 117602, Singapore 123 J Fusion Energ (2015) 34:435–442 DOI 10.1007/s10894-014-9813-3