US researchers claim vast data-density increase

Researchers at two US universities say they have developed a technique that could result in storage densities of 10 terabits per square inch.

According to one of the researchers, Ting Xu of the University of California at Berkeley, the density achievable with the technology "could potentially enable the contents of 250 DVDs to fit onto a surface the size of a quarter" — about the size of a UK 10p coin.

The innovation uses a technique in which nanoscale elements precisely assemble themselves over large surfaces. This approach could soon open doors to dramatic improvements in the data-storage capacity of electronic media, according to the two researchers involved.

"I expect that the new method we developed will transform the microelectronic and storage industries, and open up vistas for entirely new applications," said the joint-leader of the project, Thomas Russell of the University of Massachusetts at Amherst. "This work could possibly be translated into the production of more energy-efficient photovoltaic cells, for instance."

The researchers used a technique involving the molecules in a thin film of block copolymers, which consist of two or more chemically dissimilar linked polymer chains, that self-assemble into a precise, equidistant pattern when spread out on a surface.

"For more than a decade researchers have been trying to exploit this characteristic for use in semiconductor manufacturing, but they have been constrained because the order starts to break down as the size of the area increases," the universities said in a statement. Once the formation breaks down, the individual domains cannot be read or written to, rendering them useless as a form of data storage.

To overcome this size issue, the researchers thought of "the relatively simple solution" of using sapphire crystal which, when cut at an angle and heated to 1,300°C to 1,500°C for 24 hours, will reorganise itself into a highly ordered pattern of "sawtooth" ridges that can then be used to guide the self-assembly of the block polymers.

With this technique, the researchers say, they were able to achieve defect-free arrays with parts as small as 3nm, which is the equivalent of 10 terabits per square inch.

Because crystals come in a variety of sizes, there are few limitations on how large this block copolymer array can be produced, the researchers said. They also noted that the angle and depth of the sawtooth ridges can be easily varied by changing the temperature at which the crystal is heated, to fine-tune the desired pattern.

"We can generate nearly perfect arrays over macroscopic surfaces where the density is over 15 times higher than anything achieved before," Russell said.

The researchers are looking into techniques to develop their research and explore the possibilities of photo lithography and high-capacity data storage on devices such as DVDs.