Kinetic and thermodynamic measurements of the crystallization of phase change materials using transmission electron microscopy and nanocalorimetry

Phase change materials (PCM) are semiconducting alloys with distinct optical and electrical properties in the amorphous and crystalline phases that make them useful for memory applications. The thermodynamics and kinetics of the crystallization of PCMs far from equilibrium conditions are of technological and scientific interest but can be difficult to probe experimentally due to small grain sizes and very rapid crystal growth. In this work, the crystallization of an amorphous PCM, Ag₃In₄Sb₇₆Te₁₇, was investigated using transmission electron microscopy (TEM) imaging and a nanocalorimeter designed for use in a TEM. In situ TEM imaging was used to resolve crystal growth of small grains. Nanocalorimetry experiments were run at multiple heating rates (up to 10⁴ K/s) and a Kissinger analysis was used to find the activation energy of crystallization. The thermodynamic measurements allowed the enthalpy of fusion to be calculated for temperatures far below the equilibrium melting temperature. Current TEM imaging experiments have demonstrated the viability of planned experiments for the simultaneous collection of kinetic and thermodynamic data over a broad set of heating rates.