Memories that use heat to store information

Electronic components heat up, and this is a source of problems and energy losses. But did you know that some components use heat as a lever to store information? A team from the IEMN is investigating the thermal properties of the so-called ‘phase change’ materials used in these new types of memory. The results are published in the Journal of Applied Physics.

Phase-change memories have a number of advantages, including high miniaturization capacity, low power consumption and the ability to retain their last state after use, hence the term ‘non-volatile’.  This very useful property comes from the material used, in our case GeSbTe, a chalcogenide glass with a disordered, electrically insulating phase and conductive crystalline phases. PCM (Phase-Change Memories) use a thin layer of this material and electrodes that heat a nanometric zone of material to make the (reversible) transition between the amorphous and crystalline phases. The information is then stored and read by measuring the electrical resistance of this zone, the ‘memory point’.

This technology, already used in automotive electronics for example, involves considerable challenges in terms of materials engineering, as the memory point locally reaches temperatures more than 600°C during melting. Successfully confining such a release of heat to an area of just a few nanometers over a period of less than a microsecond requires knowledge of the material’s properties, particularly its thermal properties, as a function of temperature. Furthermore, the composition of the material is highly complex and its properties are not always known precisely.