Ion beam energy dependence of surface and structural properties of amorphous carbon films deposited by IBSD method on Ni
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jid M. Larijani and Shahab Sheibani Radiation Application Research School, Nuclear Sciences and Technology Institute, Tehran 14395836, Iran (Received 21 October 2016; accepted 11 January 2017)
The amorphous carbon thin films were deposited by the ion beam sputtering deposition technique on Ni–Cu alloy substrates. The effect of sputtering ion beam energy on wettabillity, surface, and structural properties of thin films was examined. The sputtering ion beam energy was varied over a wide range from 2 to 5 keV. Raman spectra showed that the values of ID/IG ratio and the ‘G’ peak position have a reduction trend by increasing the argon ion beam energy while the surface roughness increased due to the resputtering effect. The wettability and surface energy of a-C carbon films were studied by contact angle measurements in relation to structure and topography. The deposited films showed a relatively high water contact angle (CA) that decreases from 87° to 75°. The X-ray photoelectron spectroscopy showed that the value of sp3/sp2 bond content of a-C thin films deposited with the highest argon ion beam energy of 5 keV was about 0.8. Furthermore, the optical band gap followed similar trends of the structural properties.
I. INTRODUCTION
The binary Cu–Ni alloys are promising materials for a variety of applications such as heat exchangers and condenser tubes and thermoseeds because of their interesting properties including corrosion resistance, excellent strength, thermal conductivity, and antimicrobial. In a certain composition Cu (30–33%)–Ni (66–70%) alloy has a Curie temperature in the range of 41–46 °C which is appropriate for the production of ferromagnetic thermoseeds with a biodegradable overcoat such as an organic carbon layer.1 Amorphous carbon films containing a mixture of sp2 and sp3 bonded carbon atoms have superior properties such as biocompatibility, chemical inertness, high hardness, wear resistance, low friction coefficient, high electrical resistivity for modifying surface properties of metal substrates used in medical implants and tools, storage devices, and microelectromechanical devices.2–11 Although several studies have been done to investigate properties of amorphous carbon overcoats on metal substrates (Cu–Ni alloy, Ni, stainless steel, Monel), the differences in physical properties of substrates, deposition methods (magnetron sputtering, chemical vapor deposition and etc.), and deposition parameters make more investigations necessary.8–15 The ion beam sputtering deposition (IBSD) method that was Contributing Editor: Jürgen Eckert Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] DOI: 10.1557/jmr.2017.43
contrived by Aisenberg and Chabot in 19714 for deposition of amorphous carbon is a widely used deposition technique for production of overcoats with good adhesion to a substrate because of simultaneous deposition by ion implantation.16 Thus, a gradual strain transition from substrate to deposited film can be created and less builtin strain in the deposited fi
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