Novel hybrid facing targets sputtered amorphous carbon overcoat for ultra-high density hard disk media W.C. Poh a,b , S.N. Piramanayagam a, ⁎ , J.R. Shi a , T. Liew a,b a Data Storage Institute, 5 Engineering Drive 1, Singapore 117608, Singapore b Department of Electrical and Computer Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260, Singapore Received 21 April 2006; received in revised form 11 July 2006; accepted 14 July 2006 Available online 12 September 2006 Abstract Amorphous carbon films form a critical protective layer on magnetic hard disk media. A novel in-house configured hybrid facing targets sputtering (HyFTS) utilizing a special magnetron arrangement was used to deposit amorphous carbon (a-C) overcoats. The corrosion inhibition ability and mechanical property were investigated and compared with that of the a-C overcoats deposited by conventional magnetron sputtering (CMS). Studies were done using electrochemical techniques and nano-scratch analysis to determine how corrosion inhibition ability changes at thickness of 2 nm and 5 nm and the scratch resistance of the two types of a-C overcoats, respectively. Electrochemical impedance spectroscopy and potentiodynamic polarization investigations have shown that a-C films deposited by HyFTS have good corrosion resistance even at 2 nm thickness. But at 2 nm, CMS deposited a-C overcoat shows sign of corrosion. Nano-scratch test has also shown improved scratch resistance of the HyFTS deposited a-C. This may be attributed to the better quality film with higher sp 3 content deposited by HyFTS as a result of it having a higher amount of ionized species generated. © 2006 Elsevier B.V. All rights reserved. Keywords: Amorphous carbon; Sputtering; Corrosion; Coatings 1. Introduction The potential applications of diamond-like carbon, namely amorphous carbon film, in various fields have made it a very attractive and useful material. The corrosion inhibition pro- perties of such thin films have been used in a significant number of applications, such as in magnetic disk as a protective over- coat, as an electrode material for sensors, and as a biocompat- ible and corrosion coating for biomaterials. Out of the many important uses of amorphous carbon, its application as a corrosion protection overcoat for magnetic storage media will be investigated in this research. The demand for storage media with greater storage capacity has resulted in the rapid increase in the recording density of hard disk drives. This rate of increase has been very significant especially in recent years. With an increase in the areal density, a reduction of the magnetic spacing is required. One way of achieving this magnetic spacing reduction is by reducing the thickness of the disk overcoat. It was reported that for ultra-high recording density (e.g. 500 Gbit/in. 2 and above), the magnetic spacing should be about 6.5 nm and the corresponding thickness of the disk overcoat would be in the sub-2 nm range [1]. To reduce the thickness of the disk overcoat, re- searchers have generally focused their research efforts in two main areas. Some have worked on improving deposition tech- niques to fabricate thin carbon films with enhanced properties [2–5] while others have concentrated on looking for alternative overcoat materials [1,6]. In this work, hybrid facing targets sputtering (HyFTS) using a novel in-house modified magnetron arrangement was em- ployed to deposit amorphous carbon (a-C) overcoats. The effectiveness of the ultra-thin HyFTS deposited a-C overcoat in inhibition of corrosion was investigated and was compared to that of the conventional magnetron sputtering (CMS) deposited a-C using both potentiodynamic polarization and electrochem- ical impedance spectroscopy (EIS). Diamond & Related Materials 16 (2007) 379 – 387 www.elsevier.com/locate/diamond ⁎ Corresponding author. Tel.: +65 68748550; fax: +65 67772406. E-mail address: Prem_SN@dsi.a-star.edu.sg (S.N. Piramanayagam). 0925-9635/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.diamond.2006.07.020.