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Fragile‐to‐Strong Crossover in Supercooled Liquid Ag‐In‐Sb‐Te Studied by Ultrafast Calorimetry
Author(s) -
Orava Jiri,
Hewak Daniel W.,
Greer A. Lindsay
Publication year - 2015
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201501607
Subject(s) - supercooling , materials science , chalcogenide , crystallization , nucleation , calorimetry , phase (matter) , chemical physics , thermodynamics , differential scanning calorimetry , glass transition , optoelectronics , chemistry , organic chemistry , composite material , polymer , physics
Phase‐change random‐access memory relies on the reversible crystalline‐glassy phase change in chalcogenide thin films. In this application, the speed of crystallization is critical for device performance: there is a need to combine ultrafast crystallization for switching at high temperature with high resistance to crystallization for non‐volatile data retention near to room temperature. In phase‐change media such as nucleation‐dominated Ge 2 Sb 2 Te 5 , these conflicting requirements are met through the highly “fragile” nature of the temperature dependence of the viscosity of the supercooled liquid. The present study explores, using ultrafast‐heating calorimetry, the equivalent temperature dependence for the growth‐dominated medium Ag‐In‐Sb‐Te. The crystallization shows (unexpectedly) Arrhenius temperature dependence over a wide intermediate temperature range. Here it is shown that this is evidence for a fragile‐to‐strong crossover on cooling the liquid. Such a crossover has many consequences for the interpretation and control of phase‐change kinetics in chalcogenide media, helping to understand the distinction between nucleation‐ and growth‐dominated crystallization, and offering a route to designing improved device performance.