Fragile-to-Strong Crossover in Supercooled Liquid Ag-In-Sb-Te Studied by Ultrafast Calorimetry

Orava, J 
Orava, J 
Hewak, DW 
Greer, AL 
Greer, AL 

Change log

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 Ge2Sb2Te5, 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.

Publication Date
Online Publication Date
Acceptance Date
chalcogenide glasses, crystallization, fragile-to-strong crossover, phase-change memory, ultrafast calorimetry
Journal Title
Advanced Functional Materials
Journal ISSN
Volume Title
Engineering and Physical Sciences Research Council (EP/M015130/1)
J.O., D.W.H. and A.L.G. acknowledge support from the Engineering and Physical Sciences Research Council (EPSRC, UK), D.W.H. in part through the EPSRC Centre for Innovative Manufacturing in Photonics. J.O. and A.L.G. acknowledge support from the World Premier International Research Center Initiative (WPI), MEXT, Japan. C. A. Angell, L. Battezzati, G. Dalla Fontana and M. Salinga are thanked for helpful discussions.