Glass Transition of the Phase Change Material AIST and its Impact on Crystallization

TL;DR

This study investigates how the crystallization behavior of the phase change material AIST varies with heating rate, revealing a transition from glassy to liquid-like crystallization and its implications for data storage.

Contribution

It provides the first detailed calorimetric analysis of AIST's crystallization kinetics across a wide range of heating rates, highlighting the transition point and activation energy changes.

Findings

Crystallization from glassy phase occurs below 5,000 K/s heating rate.

Crystallization activation energy drops above the glass transition.

Rapid crystallization enabled at high temperatures due to activation energy change.

Abstract

Engineering phase change materials (PCM) to realize superior data storage devices requires a detailed understanding of crystallization kinetics and its temperature dependence. The temperature dependence of crystallization differs distinctly between crystallizing from the glassy phase and the undercooled liquid (UCL). Hence, knowing the phase from which crystallization occurs is necessary for predicting the switching ability. Here, we measure the glassy dynamics and crystallization kinetics using calorimetry for heating rates spanning over six orders of magnitude. Our results show that the prominent PCM (Ag,In)-doped Sb2Te (AIST) exhibits a change from crystallizing from the glassy phase to crystallizing from the UCL at a critical heating rate of 5,000 K/s. Above the glass transition, the activation energy of crystallization changes drastically enabling rapid crystallization at elevated temperatures.