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The world on a postcard

May 14, 2004

Keeping up with the information flood demands storage media that are as dense and durable as possible. A solution being developed by researchers in Dresden uses modified films containing diamond-like carbon, resulting in fifty times more storage capacity than the best disk drives.

The basic principle of data storage revolves around the permanent modification of specific material characteristics. This requires a suitable instrument to read and write the data. CDs and DVDs use tiny pits and laser technology to store information. Hard drives save data within minuscule magnetic domains that the read/write head creates, reads or deletes. Whatever the medium, there are physical limits to storage density. With optical storage, density is restricted by the laser wavelength. Hard drive capacity is limited by the size of the magnetic particles. Below a certain particle size, the movement of atoms in the material causes its magnetic properties, and hence the data, to be lost.

Researchers at the Fraunhofer Institute for Material and Beam Technology IWS in Dresden have developed a new approach based on diamond-like carbon films. For the instrument, ultra-fine metal tips like those found in scanning tunneling microscopes (STM) are used. Thomas Mühl, physicist at the Leibniz Institute for Applied Physics and Materials Research IFW in Dresden, which is cooperating with the IWS, bombards the carbon film with electrons from the STM tips to create graphite trenches in the material, which in its original state is not a very good electrical conductor.

"The tiny trenches, less than 10 nanometers wide, are not only more conductive, they also project above the surface of the smooth film," explains Mühl who adds, "Both effects can be used to store information. The STM needle serves as a combined write and read instrument, albeit a slow one. The high mechanical, thermal and chemical stability of carbon ensures that the data can be safely stored for long periods of time."

Besides digital data, the researchers are looking at the possibility of storing and retrieving analog images. This is of particularly interest for long-term archiving since the method does not require digital conversion programs, which may one day become outdated or not even be available any more. A vivid example of the potential is a portrait photograph just 1.2 micrometers high. By purely mathematical calculation, 6.2 billion such passport photos - the entire human population - would fit on the surface of a postcard. In the lingo of the data storage developer, this equates to a storage density of over 5,000 gigabits per square inch. Today's top magnetic hard drives can achieve two percent of this capacity; commercially available drives a mere one percent. The two institutes are working together with Fraunhofer spin-off Arc Precision GmbH to transform the concept into a workable storage technology.

Fraunhofer-Gesellschaft