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ScienceDirect Materials Today: Proceedings 5 (2018) 20899–20903
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ICSEM 2016
Development and analysis of tantalum nitride coatings prepared by DC reactive sputtering Akash A. Gandhia,Kamlesh V. Chauhana, Jaydeep M. Kapoparab, Nayan N. Jariwalaa,Sushant K. Rawalc* a
CHAMOS Matrusanstha Department of Mechanical Engineering, Chandubhai S. Patel Institute of Technology (CSPIT), Charotar University of Science and Technology (CHARUSAT), Changa-388421, Gujarat, India. b Department of Mechanical Engineering, Alpha College of Engineering and Technology, Khatraj-382721, Gujarat, India. c McMaster Manufacturing research Institute, Department of Mechanical Engineering, McMaster University,1280 Main Street West, Hamilton, ON, L8S 4L7, Canada.
Abstract The objective of the present work is to investigate the effect of DC power variation on structural, wettability and tribological properties of tantalum nitride coatings deposited by DC reactive magnetron sputtering. The X-ray diffraction graphs of tantalum nitride coating show evolution of various textures of tantalum nitride with an increase in DC power. Wettability test showed promising results for hydrophobicity as the DC power supply was increased from 230 to 430W. The lowest contact angle of 95.6° was achieved at DC power of 230W and the highest contact angle of 100.2° was achieved at 430W. The wear test was done on uncoated and tantalum nitride coated cylindrical pins of brass and mild steel. The pins showed improvement in wear resistance when coated with tantalum nitride. © 2018 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of INTERNATIONAL CONFERENCE ON SMART ENGINEERING MATERIALS (ICSEM 2016). Keywords:Tantalum nitride; Wear; Tribology; Hydrophobic; Wettability
1. Introduction Tantalum nitride coatings are recognized as chemically inert[01], corrosion resistant and hard material [02].They are used as decorative coatings [02], dielectriclayers [03], adhesion promoters in the microelectronics industry and * Corresponding author. Tel.: +1 647 673 8701 E-mail address:
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2214-7853© 2018 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of INTERNATIONAL CONFERENCE ON SMART ENGINEERING MATERIALS (ICSEM 2016).
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fabrication of resistor elements with enhanced long-term stability [04, 05].Tantalum nitride coatings have also become technologically important as functionalized optical coatings and wear resistant coatings. There are various techniques used for depositing tantalum-based coatings like PECVD (plasma enhanced chemical vapour deposition), electron beam evaporation powders by amination, sol-gel method, DC magnetron sputtering, etc. Some applications relevant to them are decorative coating, photocatalytic surface or dielectric devices [06]. Tantalum nitride is used as a wear and corrosion-resistant materials, thin film resistors, high-speed thermal printing head and diffusion barrier [07]. The literature exploring wettability and tribological properties of tantalum nitride coatings are very limited. So the aim of this research work is to develop tantalum nitride coatings by using reactive magnetron sputtering. The change in structural, wettability and tribological properties of tantalum nitride coatings are reported in this paper. 2. Experimental A custom designed chamber (Excel Instruments, India) has been used to deposit tantalum nitride coatings on glass substrates by direct current (DC) reactive magnetron sputtering. A 2” diameter and 5 mm thick sputtering target of tantalum with 99.99% purity was used for sputtering. The target to substrate distance was kept constant at 50 mm for all depositions. Nitrogen was used as reactive gas and argon was used as an inert gas. The ratio of the gas mixtures was controlled and measured using mass flow controller and capacitance manometers (MKS) respectively. The temperature was kept at 550°C, the nitrogen and argon flow rate were kept at 18sccm each and the base pressure was kept at 4×10−4 Pa for all depositions. The deposition time and sputtering pressure were kept at 60min and 1.75Pa respectively. The power supply was kept at different values of 230W, 280W, 330W, 380W, and 430W accordingly, the sample names are given as D230, D280, D330, D380, and D430 respectively. The structural morphology of tantalum nitride coatings was examined by Bruker D8 Advance X-ray diffractometer (XRD). The surface morphology of tantalum nitride coatings was characterized by Scanning Electron Microscopy (ZEISS, EVO-18). The wettability studies of tantalum nitride coatings were done by Rame-Hart model 290 goniometer. The tribological studies were done by a pin on disc tribometer system (DUCOM) to find wear of uncoated and tantalum nitride coated brass and mild steel pins. 3. Results and Discussion The XRD patterns for tantalum nitride coatings deposited at the different power supply of 230W, 280W, 330W, 380W& 430W is shown in Fig. 1. When the power is kept at230W, (002), (111) and (202) peaks of tantalum nitride are observed.
Fig.1XRD graphs of tantalum nitride coatings deposited at different DC power.
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At DC power of 330W and 380W, only (002) and (111) peaks of tantalum nitride are observed and (202) peak disappears. The peaks observed at power value of 430W are (111) and (200) of tantalum nitride whereas (002) peak is not observed. The average crystallite size for tantalum nitride coatings increases from 39nm to 74nm as power decreases from 430W to 230W. It is reported that with an increase in flowrate from 20sccm to 80sccm, the intensity of (111) peak decreases along with the peak of (112)[08]. Moreover, it is also reported that with an increase in flow rate from 2sccm to 25sccm, intensity of (111) peak for TaN coating decreases. At nitrogen flowrate of 2sccm, the maximum intensity peak for TaN is observed and small intensity peak of (200) is evolved for tantalum nitride coating. At flowrate of 20sccm, the intensity of (111) peak decreases and evolution of (220), (311) & (222) peaks for tantalum nitride coating are observed[09]. So the observed peaks for deposited tantalum nitride coatings are in agreement with literature. The surface topography of tantalum nitride coatings was investigated by scanning electron microscopy. The micrograph of tantalum nitride coatings deposited at different DC power of 230W, 330W and 430W are shown in Fig. 2. It was noticed that grain size and surface morphology of tantalum nitride coatings changes with variation of DC power.
Fig.2 SEM Images of tantalum nitride coatings deposited at different power values of (a) 230W (b) 330W and (c) 430W.
The contact angle and surface energy values for tantalumnitride coatings deposited at different DC power values of 230W, 280W, 330W, 380W, and 430W is shown in Fig. 3.
Fig. 3 Contact angle and surface energy of tantalum nitride coatings deposited at different DC power.
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The lowest contact angle of 95.6° was achieved at DC power of 230W. When the power supply increases, the contact angle values also increases giving highest contact angle of 100.2° at DC power of 430W. The contact angle and surface energy are inversely related to each other. So the highest surface energy was obtained at lower power supply value of 230W whereas lowest surface energy was observed at DC power of 430W.
Fig. 4 Wear of uncoated and tantalum nitride coated (a) brass pins and (b) MS pins
The wear test was done on uncoated and tantalum nitride coated cylindrical pins of brass and mild steel at DC power values of 230W, 330W, and 430W.Pins were subjected to wear with the rubbing action between pins and the rotating disc at load values of 5N, 15N and 15N at different speeds of 450rpm, 500rpm, and 550rpm. The wear of uncoated and tantalum nitride coated cylindrical pins of brass and mild steel at DC power values is shown in Fig. 4. The wear of sample D430 is higher than other samples as observed from Fig. 4.Moreover, wear of brass pins is lower than that of mild steel pins. The minimum wear for uncoated and tantalum nitride coated cylindrical pins of brass and mild steel was observed at a load of 5N load and 450rpm speed. 4. Conclusion The average crystallite size of tantalum nitride coatings decreases with the increase of tantalum target power. The change in morphology is observed for tantalum nitride coatings with a change in DC power values. The surface energy decreases with increase in contact angle from 95.6° to 100.2° and DC power. Coated brass and MS pins showed minimum wear at a load of 5N and speed of 450 rpm compared to uncoated pins. 5. Acknowledgement This work has been supported by AICTE grant number 20/AICTE/RIFD/RPS (POLICY-III) 24/2012-13 sanctioned under Research Promotion Scheme (RPS). We are thankful to President and Provost of CHARUSAT for supporting this research work. We are thankful to Head, Dr. K. C. Patel Research and Development Centre (KRADLE) affiliated to Charotar University of Science and Technology (CHARUSAT), India for granting permission to use various equipment’s available in their characterization laboratory. 6. References [01] T. Elangovan, S. Murugeshan, D. Mangalaraj, P. Kuppusami, S. Khan, C. Sudha, V. Ganesan, R. Divakar, E. Mohandas, "Synthesis and High temperature XRD studies of tantalum nitride thin films prepared by reactive pulsed dc magnetron sputtering", Journal of Alloysand Compounds, 509, pp. 6400-6407, 2011.
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[02] O. Banakh, P. A. Steinmann, & L.Dumitrescu-Buforn, "Optical and mechanical properties of tantalum oxynitride thin films deposited by reactive magnetron sputtering", Thin Solid Films, 513(1-2), pp.136–141, 2006. [03] D. Cristea, A. Crisan, D. Munteanu, M. Apreutesei, M.F. Costa, & L. Cunha, "Tantalum Oxynitride Thin Films: Mechanical properties and wear behavior dependence on growth conditions", Surface & Coatings Technology, 258, pp.587-596, 2014. [04] M. Grosser, U. Schmid, “The impact of sputter conditions on the microstructure and on the resistivity of tantalum thin films", Thin Solid Films 517 pp. 4493–4496, 2009. [05] D. Cristea, A. Crisan, N. Cretu, J. Borges, C. Lopes, L. Cunha, V. Ion, M. Dinescu, N.P.Barradas, E. Alves, M. Apreutesei, D. Munteanu, "Structure dependent resistivity and dielectric characteristics of tantalum oxynitride thin films produced by magnetron sputtering" Applied surface science 354, pp. 298-305, 2015. [06] A. Zaman, "Characterization of Tantalum Nitride Thin Films Synthesized by Magnetron Sputtering", M.S. 2014. [07] D. K. Kim, H. Lee, D. Kim, Y. K. Kim, "Electrical and Mechanical properties of tantalum nitride thin films deposited by reactive sputtering", Journal of crystal growth, 283,pp. 404-408, 2005. [08] M. Grosser, M. Munch, H.Seidal, C. Bienert, A. Roosen, U. Schmid, "The impact of substrate properties and thermal annealing on tantalum nitride thin films", Applied Surface Science, 258, pp. 2894-2900, 2012. [09] T. Elangovan, S. Murugeshan, D. Mangalaraj, P. Kuppusami, Shabhana Khan, C. Sudha, V. Ganesan, R. Divakar, E. Mohandas, "Synthesis and high temperature XRD studies of tantalum nitride thin films prepared by reactive pulsed dc magnetron sputtering", Journal of Alloy & comp., 509,pp. 6400-6407, 2011.