Publication Date:
2016-05-18
Description:
The temperature-dependent viscosity η ( T ) is measured for the equilibrium liquid of the chalcogenide Ag–In–Sb–Te (AIST), the first time this has been reported for a material of actual interest for phase-change memory. The measurements, in the range 829–1254 K, are made using an oscillating-crucible viscometer, and show a liquid with high fragility and low viscosity, similar to liquid pure metals. Combining the high-temperature viscosity measurements with values inferred from crystal growth rates in the supercooled liquid allows the form of η ( T ) to be estimated over the entire temperature range from above the melting point down to the glass transition. It is then clear that η ( T ) for liquid AIST cannot be described with a single fragility value, unlike other phase-change chalcogenides such as liquid Ge–Sb–Te. There is clear evidence for a fragile-to-strong crossover on cooling liquid AIST, similar to that analyzed in Te 85 Ge 15 . The change in fragility associated with the crossover in both these cases is rather weak, giving a broad temperature range over which η ( T ) is near-Arrhenius. We discuss how such behavior may be beneficial for the performance of phase-change memory. Consideration of the fragile-to-strong crossover in liquid chalcogenides may be important in tuning compositions to optimize the device performance.
Print ISSN:
0021-9606
Electronic ISSN:
1089-7690
Topics:
Chemistry and Pharmacology
,
Physics
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