Influence of nitrogen flow rates on materials properties of CrN x films grown by reactive magnetron sputtering
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Influence of nitrogen flow rates on materials properties of CrN x films grown by reactive magnetron sputtering B SUBRAMANIAN∗ , K PRABAKARAN and M JAYACHANDRAN Electrochemical Materials Science Division, CSIR- Central Electrochemical Research Institute, Karaikudi 630 006, India MS received 9 April 2011; revised 17 October 2011 Abstract. Chromium nitride (CrN) hard thin films were deposited on different substrates by reactive direct current (d.c.) magnetron sputtering with different nitrogen flow rates. The X-ray diffraction patterns showed mixed Cr2 N and CrN phases. The variations in structural parameters are discussed. The grain size increased with increasing nitrogen flow rates. Scanning electron microscopy image showed columnar and dense microstructure with varying nitrogen flow rates. An elemental analysis of the samples was realized by means of energy dispersive spectroscopy. The electrical studies indicated the semiconducting behaviour of the films at the nitrogen flow rate of 15 sccm. Keywords.
Thin films; magnetron sputtering; chromium nitride; X-ray diffraction.
1. Introduction Surface modification by means of thin film deposition is an important industrial process which is used to protect base materials against wear, fatigue, corrosion and many other surface related damage phenomena (Olaya et al 2007). Transition metal nitrides having bonds of a mixed nature of covalent, ionic and metallic character are of technological importance due to the combination of their functional properties that are associated with their unusual electronic bonding such as high hardness, high melting point and oxidation resistance (Olaya et al 2005). These coatings have found widespread use as hard wear protective coatings for cutting tools and wear applications, as diffusion barriers in micro electronic applications, and as corrosion and abrasion-wear resistant layers on optical and mechanical components (Deniel et al 2009). TiN and CrN are the most extensively investigated hard coatings. It is known that TiN coatings are not always corrosion resistant due to the micro defect in the coatings. CrN coatings exhibit relatively dense microstructure and provide high wear and corrosion resistance (Grips et al 2006). In PVD coatings, intrinsic stress is generated by reactions, phase formations, energetic particle bombardment, etc. The change in temperature differential in the expansion or contraction of dissimilar layered materials results in a variation of the residual stress along the thickness direction. The stress translates between the coating and the substrate interface, causing the coated system to contract, elongate or bend. Buckling may occur only at a critical value of compressive stress. The stress depends on thickness of the materials. A great advantage of CrN is that the internal stresses
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are very low, due to which coatings with thickness of more than 40 μm can be obtained on a variety of engineering substrates. On the other hand, TiN coatings can be deposited only wi
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