Approaching the Glass Transition Temperature of GeTe by Crystallizing Ge 15 Te 85

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 Ge 15 Te 85 . 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.