Effect of radio frequency and direct current modes of deposition on protective metallurgical hard silicon carbon nitride coatings by magnetron sputtering

doi:10.1016/j.vacuum.2009.06.051

Vacuum

Volume 83, Issue 12, 11 August 2009, Pages 1464-1469

https://doi.org/10.1016/j.vacuum.2009.06.051 Get rights and content

Abstract

Siliconcarbonitride (Si–C–N) coatings were deposited on silicon (100) by magnetron sputtering using radio frequency alternating current and direct current. The mechanical performance of the coatings in the two modes was compared through static indentation and scratch test in both microlevel and nanolevel. A structure–property correlation was attempted to establish mechanical behavior, microstructure and bond present in the film. Studies showed RF films to be mechanically tougher and having higher scratch resistance compared to the DC films.

Introduction

Hard coatings are required for the protection of machine parts under wear and abrasion. Conventional superhard coatings of diamond, cBN, transition metal carbides and nitrides are expensive and brittle and cannot be used at high temperatures [1], [2]. Nanocomposite and multilayer coatings are the alternatives with consecutive alternate layers of low and high elastic modulus which results in the inhibition of dislocation motion giving high hardness along with toughness [3], [4]. Si–C–N nanocomposite coatings have shown improved properties like thermal stability (up to 1500 °C), oxidation resistance, high hardness, wide band gap, chemical inertness, excellent mechanical, thermal and optical properties [5], [6], [7], which make them a promising material for wear and oxidation resistance, optoelectronics, MEMS and high temperature applications [8], [9], [10], [11], [12], [13], [14]. Si–C–N system is expected to have different superhard phases in amorphous Si–C–N matrix namely SiC, β-Si₃N₄ and even β-C₃N₄ phase. Chemical vapour deposition, magnetron sputtering, microwave and electron cyclotron resonance PECVD, ion implantation and pulsed laser deposition processes have been used to fabricate Si–C–N films. Out of all these processes, sputtering is a promising technique for deposition of good, adherent coatings and to tailor the properties of films by varying deposition conditions. The deposition conditions, electric source such as radio frequency (RF) or direct current (DC), used influence the ultimate properties of the coatings to a good extent. Due to alternate current cycles in RF, the deposition rate is lower compared to the DC mode. Therefore the time span available for the adatoms to undergo thermal accommodation and coalescence at the substrate is different in both the cases, which affects the properties of the coatings deposited in the two different modes. To our knowledge such comparative study on Si–C–N is not available. We report our studies on the effect of electric sources such as RF and DC during magnetron sputtering of nanocomposite Si–C–N film on microstructural and mechanical properties.

Section snippets

Experimental procedures

Si–C–N coatings were deposited on Si (100) and SS 304 substrates by RF and DC magnetron sputtering (HHV, Bangalore, India) using single SiC target of 50 mm diameter and 3 mm thickness, made by sintering SiC powder compacted into disc and sintering at 1950 °C in graphite furnace, under argon and nitrogen atmosphere. The base pressure of the chamber, prior to deposition of film, was 5 × 10⁻⁴ Pa and during deposition argon was fed into the chamber up to 0.1 Pa and rest nitrogen was introduced to reach

Results and discussions

A higher deposition rate of 0.56 nm/s was obtained in the case of DC compared to RF deposited (0.22 nm/s) Si–C–N films. The times were accordingly adjusted to have a film thickness of around 4 μm.

The field emission SEM (FESEM) studies of the films deposited on silicon and steel substrates for both DC and RF modes are shown in Fig. 1. The cross-sectional micrographs of the films deposited in both RF and DC modes on silicon substrates are give in Fig. 1(a) and (b). Columnar growth arising from high

Conclusions

In conclusion, higher deposition rate of 0.56 nm/s was obtained in case of the DC compared to RF deposited (0.22 nm/s) Si–C–N films. The lowering of the deposition rate and increasing the deposition time aided in nitrogen and silicon incorporation into the film which was the reason for the finer grains in RF, lower surface roughness and also percentage C–N phase compared to DC mode film, which had metallic Si phase too along with SiC and C₃N₄ phase. These led to higher hardness and modulus of the

Acknowledgements

The authors acknowledge the grant received for the work from DST, India under nanoinitiative program and Prof. I. Manna, IIT Kharagpur, India, for FESEM.

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Effect of radio frequency and direct current modes of deposition on protective metallurgical hard silicon carbon nitride coatings by magnetron sputtering

Abstract

Introduction

Section snippets

Experimental procedures

Results and discussions

Conclusions

Acknowledgements

Thin Solid Films

Diamond Relat Mater

Sens Actuators A Phys

Compos Sci Technol

Appl Surf Sci

Surf Coat Technol

Diamond Relat Mater

Mater Lett

Thin Solid Films

The material science of thin films

Transition metal carbides and nitrides