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DS: Dünne Schichten

DS 31: Postersitzung

DS 31.31: Poster

Tuesday, March 27, 2001, 16:30–17:30, Foyer Saal 4

Structural transformations of Ge₄Sb₁Te₅, Ge₂Sb₂Te₅ and AgInSbTe films studied by electrical resistivity measurements and X-Ray diffraction — •Walter K. Njoroge, Ine’s Friedrich, and Matthias Wuttig — I.Physikalisches Institut der RWTH Aachen, 52056 Aachen, Germany

Temperature dependent measurements of electrical resistance have been employed to study the kinetics of structural changes of sputtered Ge₄Sb₁Te₅, Ge₂Sb₂Te₅ and AgInSbTe films. These materials can be characterized by two stable physical phases that exhibit significantly different optical properties. Hence, they are of great interest in the phase-change media technology since they enable to write, erase and rewrite information repetitively using optical techniques.Upon annealing a major resistivity drop is observed which can be attributed to structural changes as corroborated by X-ray diffraction. This enabled a precise determination of transition temperatures and activation energies. With increasing temperature both Ge₄Sb₁Te₅ and Ge₂Sb₂Te₅ films first change from an amorphous to a rock salt structure at around 157∘ C and 140∘ C, respectively. A second transition from rock salt to hexagonal phase is observed at 310∘ C for Ge₂Sb₂Te₅ films. The transition from amorphous to crystalline AgInSbTe films is observed at a temperature of 169∘ C. By applying Kissinger’s method the activation energies for crystallization to the rock salt structure are determined to be 3.72 eV and 2.24 eV for Ge₄Sb₁Te₅ and Ge₂Sb₂Te₅, respectively. Values of 3.64 eV and 3.3 eV are obtained for the phase transformation to the hexagonal phase for Ge₂Sb₂Te₅ and AgInSbTe, respectively.