Smallest Phase-Change Material To Date

To build fast smartphones and tablet computers that can store troves of data, some engineers have tinkered with memory devices that rely on phase-changing chalcogenide materials. With a little pulse of heat, these materials quickly morph between crystalline and amorphous states, which serve as 1s and 0s in memory cells. Researchers have now developed a synthesis technique leading to the smallest working phase-change material yet: one-dimensional germanium-telluride nanowires with diameters less than 2 nm (Nano Lett. 2013, DOI: 10.1021/nl4010354). To make the nanowires, Cristina E. Giusca of the U.K.’s National Physical Laboratory and her team used carbon nanotubes as templates, filling the inner cores of the nanotubes with molten GeTe using capillary action. They showed that the resulting amorphous GeTe nanowires can be converted to the crystalline state and back again when heated by a beam of electrons. Giusca thinks the wires could lay the foundation for completely novel architectures for memory devices. Her team is currently working toward integrating the nanowires into simple devices.