Improvement in cyclic operation of unit pixel device using Sb-excess Ge₂Sb₂Te₅ thin films for hologram image implementation

The effects of the atomic composition of Ge₂Sb₂Te₅ (GST), especially the Sb-excess phase, on device reliability were investigated for applications of spatial light modulator (SLM) devices using phase-change materials. Sb-excess GST phases were prepared by cosputtering with two target systems. For Sb-excess GST thin films, amorphous phases were found to be more directly crystallized to more conductive hexagonal-close-packing phases at higher crystallization temperatures without the appearance of a less conductive face-centered-cubic phase with increasing amount of incorporated Sb. The marked changes in crystallization behavior and improved thermal stability were suggested as critical benefits for enhancing the device durability during cyclic operations, considering that the interdiffusion within the GST could be the main origin of the final device failure. The number of cyclic operations of the unit pixel device was markedly improved to more than 10³ when the amount of excess Sb was modulated from 0 to 21 at. %.