CHICAGO US researchers have developed ultrathin films that when sandwiched together form a superconductor, an advance that could lead to a new class of fast, power-saving electronics.

The films can be used at relatively high temperatures for superconductors, making them easier to handle and produce, they said on Wednesday.

'What we have done is we have put together two materials, neither of which is a superconductor, and we found their interface -- where they touch -- is superconducting,' said physicist Ivan Bozovic of the US Department of Energys Brookhaven National Laboratory.

'This superconducting layer is extremely thin. It is thinner than 1 nanometer, which is 1 billionth of a meter,' added Bozovic, whose findings appear in the journal Nature.

'It opens vistas for further progress, including using these techniques to significantly enhance superconducting properties in other known or new superconductors.'

Like their name implies, superconductors are useful because they are extremely efficient at conducting electricity.

If cooled to the materials critical operating temperature, they have no resistance to the flow of electrical current, unlike ordinary electrical wires, which can eventually overheat.

The superconductors used in a magnetic resonance imaging or MRI machine, for example, must be cooled with liquid helium to keep them at 4 on the Kelvin scale, or near absolute zero minus 452.47 degrees Fahrenheit (minus 269.15 degrees Celsius).

The superconducting film developed by scientists at Brookhaven, however, work at temperatures of 50 Kelvin or minus 369.67 degrees Fahrenheit (minus 223.15 degrees Celsius).

'The practicality of superconductivity depends in some sense on the refrigeration you use to cool it down,' Bozovic said.

At 50 Kelvin, the superconducting film is close to the point where it could be cooled inexpensively by liquid nitrogen, which cools to 77 Kelvin or minus 321.07 degrees Fahrenheit (minus 196.15 degrees Celsius).

'It brings us one step closer to producing mass-scale superconducting electronics,' he said.

He said the ultimate goal is to develop superconducting materials that could be used at room temperature. And he thinks further study with these new ultrathin films may lend some clues on how to get there, a problem he calls 'one of the most important open problems in condensed matter physics.'