Approaching the Glass Transition Temperature of GeTe by Crystallizing Ge₁₅Te₈₅

Like many phase-change materials, GeTe crystallizes upon heating at a conventional rate before the calorimetric glass transition is reached. This has so far prevented an unambiguous determination of its glass transition temperature T_g. Herein, a new approach is realized to estimate the glass transition temperature T_g for GeTe through progressive crystallization of Ge₁₅Te₈₅. Selective crystallization of pure tellurium during sub-T_g annealing leads to a gradual change in the composition of the amorphous surrounding toward that of GeTe. This gives rise to a new endotherm whose onset temperature gradually approaches the T_g of GeTe.