Role of local structure in the phase change of Ge–Te films

Abstract

The role of structure in the crystallization of GexTe100−x model system suitable for phase-change applications is established by determining the local environment of each constituent using EXAFS analysis. Across the compositional spectrum, both constituents satisfy the (8-N) rule in the amorphous state except that the Ge atoms are surrounded by ∼3.4 neighbors in the stoichiometric composition. The estimation of homopolar Ge–Ge and Te–Te bonds indicates that chemical order is preserved less for Ge than for Te atoms. The crystallized stoichiometric film consists of Ge clusters in addition to GeTe crystals, implying that the latter has appreciable concentration of Ge vacancies.