Expanded data storage in ‘phase-change’ material

May 7, 2012
GST_diamond - 300Copy

This illustration depicts the shape of diamond tips used to apply pressure that uncovered important new properties in the memory medium GST. The inset represents the atomic structure of amorphous GST. (Credit: Ming Xu/JHU)

A team led by Johns Hopkins engineers has discovered some previously unknown properties of a common memory material, paving the way for development of new forms of memory devices that retain data more quickly, last longer and allow far more capacity than current data storage media.



“This phase-change memory is more stable than the material used in the current flash drives. It works 100 times faster and is rewritable about 100,000 times,” said the study’s lead author, Ming Xu, a doctoral student in the Department of Materials Science and Engineering in Johns Hopkins’ Whiting School of Engineering. “Within about five years, it could also be used to replace hard drives in computers and give them more memory.”



To solve this mystery, Xu and his team used another method to trigger the change more gradually. The researchers used two diamond tips to compress the material. They employed a process called X-ray diffraction and a computer simulation to document what was happening to the material at the atomic level. The researchers found that they could “tune” the electrical resistivity of the material by four orders of magnitude during the time between its change from amorphous to crystalline form.

“Instead of going from black to white, it’s like finding shades or a shade of gray in between,” said Xu’s doctoral adviser, En Ma, a professor of materialsl science and engineering.“By having a wide range of resistance, you can have a lot more control. If you have multiple states, you can store a lot more data.”


Ref.: M. Xu et al., Pressure tunes electrical resistivity by four orders of magnitude in amorphous Ge2Sb2Te5 phase-change memory alloy, Proceedings of the National Academy of Sciences, 2012, DOI: 10.1073/pnas.1119754109