|Reactive bipolar pulsed dual magnetron sputtering of ZrN films: The effect of duty cycle
|Articolo su Rivista peer-reviewed
|Year of Publication
|Rizzo, A., Valerini D., Capodieci Laura, Mirenghi L., Di Benedetto Francesca, and Protopapa Maria Lucia
|Applied Surface Science
|Bipolar pulsed dual magnetron sputtering, Chemical analysis, Coatings, Corrosion resistance, Deposition, Deposition rates, Dual magnetron sputtering, Film growth, GXRD, hardness, Magnetron sputtering, Raman analysis, Reactive sputtering, Reactive sputtering process, Sputtering, Stoichiometry, Structural and mechanical properties, Wear and corrosion resistance, Wear resistance, X ray photoelectron spectroscopy, zirconium, Zirconium nitride (ZrN)
Zirconium nitride (ZrN) coatings, due to their inherent high hardness, wear and corrosion resistance, as well as the golden color, can be attractive for a wide range of applications, such as mechanical, optical, decorative and biomedical devices. Reactive Bipolar Pulsed Dual Magnetron Sputtering (BPDMS) operating in mid-frequency range is a powerful technique for the deposition of dense coatings, free from morphological defects, at high deposition rate. In fact, the employ of mid-frequency voltage reversals allows suppressing arcs and, as a consequence, stabilizing the reactive sputtering process. Despite the success of the dual bipolar process, there are many aspects of this complex process that are not yet well understood, such as the influence of the target voltage waveforms and plasma parameters on the film growth. In order to fill this lack of knowledge, ZrN films were deposited by BPDMS with different voltage waveforms on the Zr targets and the influence of these deposition parameters on the films’ stoichiometry as well as on their structural and mechanical properties is investigated in this paper. In particular, it was found that, for duty cycle values below 33%, the hardness of the coating increases up to 31 GPa. The analysis of the chemical composition, performed by XPS, detects an almost constant value of stoichiometry along the depth-profile of each film and the N:Zr ratio increases from 1.06 to 1.20 as the duty cycle decreases. Therefore, when the N:Zr ratio is 1.06 we got a stoichiometric ZrN compound, while for N:Zr equal to 1.20 we obtained a lack of Zr atoms with respect to N atoms. Raman spectroscopy confirms the results of XPS analyzes, since it showed some features related to the structural disorder in the sample grown with the lowest duty cycle. © 2017 Elsevier B.V.
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