Graphene Enables 10X Higher Storage in HDDs

Researchers at Graphene Flagship partners the University of Cambridge, UK, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland, Empa-Swiss Federal Laboratories for Material Science and Technology, Switzerland and Graphene Flagship associate member the University of Exeter, UK, in collaboration with colleagues at CSIR-Advanced Materials and Processes Research Institute, India, National University of Singapore (NUS), A*STAR (Agency for Science, Technology and Research), Singapore, the University of Illinois and Argonne National Laboratory, US, have demonstrated that graphene can be used to produce ultra-high density HDD.

This can lead to the development of ultra-high density magnetic data storage: a big jump from the current one terabit per square inch (Tb/in²) to ten terabits over the same area.

HDDs first appeared in the 1950ies, but their use as storage devices in PCs only took off from the mid-1980s. They have become ever smaller in size, and denser in terms of the number of stored bytes. While SSDs are popular for mobile devices, HDDs continue to be used to store files in desktop computers, largely due to their favourable cost to produce and purchase.

HDDs contain 2 major components: platters and heads. Data are written on the platters using a magnetic head, which moves rapidly above the platters as they spin. The space between head and platter is continually decreasing to enable higher densities. Currently, carbon-based overcoats (COCs) – layers used to protect the platters from mechanical damages and corrosion – occupy a significant part of this spacing. The data density of HDDs has quadrupled since 1990, and the overcoats’ thickness was reduced from 12.5nm to about 3nm, which corresponds to 1Tb/in². However, a COCs’ thickness of less than one nm would be required to make a significant improvement in data storage and reach a density of 10Tb/in².

Since the current COCs lose most of their appealing properties under 2nm, Graphene Flagship researchers replaced them with 1 to 4 layers of graphene, and tested friction, wear, corrosion, thermal stability and lubricant compatibility. Beyond its unbeatable thinness, graphene fulfills all the ideal properties of an HDD overcoat: corrosion protection, low friction, wear resistance, hardness, lubricant compatibility and surface smoothness. The researchers verified that graphene enables 2x reduction in friction and provides better corrosion and wear than state-of-the-art COCs. A single graphene layer reduces corrosion by 2.5x, and multilayer graphene showed excellent performance with a decrease of wear rate by 3 orders of magnitude.

Schematic showing the hard disk covered with graphene.
For heat-assisted magnetic recording, a laser is used to heat up the magnetic recording layer to make it writeable with a conventional read/write head.
(Credit: Anna Ott)

1-4 layers of graphene were grown via chemical vapour deposition (CVD) and transferred on Co-alloy hard disk substrates as those used in current HDD technology. The Graphene Flagship researchers also transferred graphene on hard disks made of iron-platinum (FePt) as magnetic recording layer, to test HAMR – a new magnetic storage technology that enables a much higher storage density than currently available, by heating up the recording layer to high temperatures. Current COCs do not survive HAMR’s high temperatures, but stability tests confirmed that graphene can withstand HAMR-like conditions, without degradation. Thus, graphene-based overcoats used in combination with innovative technologies, such as HAMR and bit patterned magnetic recording (BPM) – a method to pattern the magnetic media in small pillars which enables high areal density – are expected to outperform current HDDs providing a data density of 10Tb/in2 or more.

“Demonstrating that graphene can serve as protective coating for conventional hard disk drives and that it is able to withstand HAMR conditions is a very important result. This will further push the development of novel high areal density hard disk drives,” says Anna Ott, Cambridge Graphene Centre, one of the authors of this study, currently based at the Graphene Flagship associate member the University of Exeter, UK.

Mar García-Hernández, leader for enabling materials, Graphene Flagship, says: “A jump in HDDs’ data density by a factor of ten and a significant reduction in wear rate are critical to achieve more sustainable and durable magnetic data recording. Graphene based technological developments are progressing along the right track towards a more sustainable world.”

Andrea C. Ferrari, science and technology officer, Graphene Flagship and chair management panel, adds: “This work showcases the excellent mechanical, corrosion and wear resistance properties of graphene for ultra-high storage density magnetic media. Considering that in 2020, around 1 billion terabytes of fresh HDD storage was produced, these results showcase the potential of graphene for the mass market. Yet again, the Graphene Flagship is at the forefront of the development of cutting-edge technologies.”

Article: Graphene Overcoats for Ultra-High Storage Density Magnetic Media

Nature Communications has published an article written by N. Dwivedi,CSIR-Advanced Materials and Processes Research Institute, Bhopal, India, Department of Electrical and Computer Engineering, National University of Singapore, Singapore, Singapore, A. K. Ott, Cambridge Graphene Centre, University of Cambridge, Cambridge, UK, and Department of Engineering, University of Exeter, Exeter, UK, K. Sasikumar, Center for Nanoscale Materials, Argonne National Laboratory, Argonne, IL, USA, C. Dou, Cambridge Graphene Centre, University of Cambridge, Cambridge, UK,R. J. Yeo, Department of Electrical and Computer Engineering, National University of Singapore, Singapore, Singapore, Institute of Materials, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland, B. Narayanan, Center for Nanoscale Materials, Argonne National Laboratory, Argonne, IL, USA, U. Sassi, D. De Fazio, G. Soavi, Cambridge Graphene Centre, University of Cambridge, Cambridge, UK, T. Dutta, Department of Electrical and Computer Engineering, National University of Singapore, Singapore, Singapore, Empa-Swiss Federal Laboratories for Material Science and Technology, Dübendorf, Switzerland, O. Balci, S. Shinde, J. Zhang, A. K. Katiyar, Cambridge Graphene Centre, University of Cambridge, Cambridge, UK, P. S. Keatley, Department of Physics and Astronomy, University of Exeter, Exeter, UK, A. K. Srivastava, CSIR-Advanced Materials and Processes Research Institute, Bhopal, India, S. K. R. S. Sankaranarayanan, Center for Nanoscale Materials, Argonne National Laboratory, Argonne, IL, USA, Department of Mechanical and Industrial Engineering, University of Illinois, Chicago, IL, USA, A. C. Ferrari, Cambridge Graphene Centre, University of Cambridge, Cambridge, UK, and C. S. Bhatia, Department of Electrical and Computer Engineering, National University of Singapore, Singapore, Singapore.

Abstract: “Hard disk drives (HDDs) are used as secondary storage in digital electronic devices owing to low cost and large data storage capacity. Due to the exponentially increasing amount of data, there is a need to increase areal storage densities beyond ~1 Tb/in². This requires the thickness of carbon overcoats (COCs) to be <2 nm. However, friction, wear, corrosion, and thermal stability are critical concerns below 2 nm, limiting current technology, and restricting COC integration with heat assisted magnetic recording technology (HAMR). Here we show that graphene-based overcoats can overcome all these limitations, and achieve two-fold reduction in friction and provide better corrosion and wear resistance than state-of-the-art COCs, while withstanding HAMR conditions. Thus, we expect that graphene overcoats may enable the development of 4–10 Tb/in² areal density HDDs when employing suitable recording technologies, such as HAMR and HAMR+bit patterned media.“

About Graphene Flagship
It is research, innovation and collaboration. Funded by the European Commission, it aims to secure a major role for Europe in the ongoing technological revolution, helping to bring graphene innovation out of the lab and into commercial applications. It gathers nearly 170 academic and industrial partners from 22 countries, all exploring different aspects of graphene and related materials. Bringing diverse competencies together,it facilitates cooperation between its partners, accelerating the timeline for industry acceptance of graphene technologies. The European Commission’s FET Flagships enable research projects on an unprecedented scale. With €1 billion budgets, the Graphene Flagship, Human Brain Project and Quantum Flagship serve as technology accelerators, helping Europe to compete with other global markets in research and innovation. With an additional €20 million investment, the European Commission has now funded the creation of an experimental pilot line for graphene-based electronics, optoelectronics and sensors.