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Graphene offers tenfold improvement on current hard disk drives, say Cambridge researchers

It is believed that about one billion terabytes of new hard disk drive data was created last year, meaning there is growing demand for improved storage mediums.

A study by Cambridge Graphene Centre has shown that graphene can be used for ultra-high density hard disk drives (HDD), and offers a tenfold improvement on current technologies.

A hard disk drive
A hard disk drive

Inside an HDD are two major components - platters and a head.

The date is written onto the platters using a magnetic head, which moves rapidly above them as they spin.

The space between the head and platter has repeatedly been cut to enable higher densities.

In current technology, carbon-based overcoats (COCs) occupy a significant part of this spacing. These COCs are layers used to protect platters from mechanical damage and corrosion.

Since 1990, there has been a fourfold improvement in the data density of HDDs and the COC thickness has reduced from 12.5 to three nanometres (nm) - a nanometre being a billionth of a metre. To put this in context, a sheet of paper is about 100,000 nanometres.

This improvement has led to storage capability corresponding to one terabyte per square inch.

Now, thanks to graphene, Cambridge researchers have multiplied this by 10.

They did it by replacing commercial COCs with one to four layers of graphene, which is an allotrope of carbon with a single layer of atoms arranged in a two-dimensional honeycomb lattice.

An engineer works on a hard disk drive
An engineer works on a hard disk drive

This provides unbeatable thinness, but graphene also fulfils all the requirements of an HDD overcoat - corrosion protection, low friction, wear resistance, hardness, lubricant compatibility and surface smoothness.

The Cambridge researchers - collaborating with teams at the University of Exeter, India, Switzerland, Singapore and the US - found a single graphene layer reduced corrosion by a factor of 2.5. There was a twofold reduction in friction and improvement in wear compared to today’s state-of-the-art solutions.

Prof Andrea C Ferrari, director of the Cambridge Graphene Centre, said: “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 one billion terabytes of fresh HDD storage was produced, these results indicate a route for mass application of graphene in cutting-edge technologies.”

The Cambridge scientists transferred graphene onto hard disks made of iron-platinum as the magnetic recording layer.

Then they tested Heat-Assisted Magnetic Recording (HAMR). This new technology, which heats the recording layer to high temperatures, further increases storage density but current COCs do not perform at these high temperatures.

Graphene does, however, meaning that when coupled with HAMR, it can outperform current HDDs and achieve more than 10 terabytes of storage per square inch.

An illustration of the molecular structure of graphene
An illustration of the molecular structure of graphene

Dr Anna Ott, from the Cambridge Graphene Centre, one of the co-authors of this study, published in Nature Communications, said: “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.

HDDs have been around since the 1950s, although they became popular for storage in personal computers from the 1980s.

2021 is predicted to be the year when shipments of solid-state drives (SSDs) outstrip HDDs for the first time.

SSDs, a flash storage medium with no mechanical parts, are used in mobile devices but also increasingly in personal computers, particularly in laptops, where their speed and durability makes them a good choice to boost start-up speeds, store operating systems and frequently-used applications. Dropping a laptop with an SSD is also less likely to result in damage than if it had an HDD.

But SSDs are more expensive, so hybrid machines team them with larger HDDs for the storage of files like photographs, videos and documents. HDDs with graphene could be a very compelling option.

Meanwhile, other innovations are on the way.

DNA has even been suggested as one storage medium of the future, while last week the Cambridge Independent reported how CMR Surgical was working with Microsoft on the concept of using glass as a storage platter that will safely retain data for 10,000 years.

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