Phase change memory should be the technology of the future. The memory secures data by changing the aggregate state of the individual bits between liquid, glassy, and crystalline. The phase change occurs through an electromagnetic field, heat, or light impulses. This technology will be used to produce fast, cost-effective and high-density memory in the future. It should also be possible to read out the memory much more frequently. This is why companies such as IBM, Samsung, and Intel are trying to convert this technology into usable products. However, it is still unclear whether this is possible.
A team of scientists from various universities has now discovered that an alloy of germanium, antimony, and tellurium is particularly suitable for the phase-change memory. Dr. Shuai Wei from RWTH Aachen and Dr. Zach Evenson from TU Munich have investigated the alloy using neutron scattering at the Heinz Maier-Leibnitz-Zentrum in Garching. Dr. Zachary Evenson explains: »The high resolution and the high flux of the time-of-flight spectrometer TOFTOF at the neutron source FRM II was necessary to see the motion of the particles«.
Contradiction to Einstein
An equation by Einstein, which he had set up in his doctoral thesis, has now been disproven: the equation describes the movement of particles like a sphere sinking into a honey jar. So far, this equation has also been adopted for phase change memory. The physicists explain that Einstein's equation does not apply at temperatures above the melting point.
Zeros and ones are generated as follows: below the phase transition, the liquid solidifies rapidly like glass and almost retains its poorly conducting state indefinitely; this is the state »0«. A targeted, short thermal pulse causes the temperature to rise rapidly: the bit changes to the conductive state »1« within nanoseconds. In this state, the liquid has a low viscosity and crystallization is very fast. A longer pulse, like from an infrared laser, and a rapid cooling process ensure the returning back to the »0« state.
The researchers have published their theses in the publication »Breakdown of the Stokes-Einstein relation above the melting temperature in a liquid phase-change material«.