Toward the Ultimate Limit of Phase Change in Ge2Sb2Te5

The limit to which the phase change memory material Ge2Sb2Te5 can be scaled toward the smallest possible memory cell is investigated using structural and optical methodologies. The encapsulation material surrounding the Ge2Sb2Te5 has an increasingly dominant effect on the material's ability to change phase, and a profound increase in. the crystallization temperature is observed when the Ge2Sb2Te5 layer is less than 6 nm chick. We have found that the increased crystallization temperature originates from compressive stress exerted from the encapsulation material. By minimizing the stress, we have maintained the bulk crystallization temperature in Ge2Sb2Te5 films just 2 nm thick.