Abstract
Phase-change materials are the basis for next-generation memory devices and reconfigurable electronics, but fundamental understanding of the unconventional kinetics of their phase transitions has been hindered by challenges in the experimental quantification. Here we obtain deeper understanding based on the temperature dependence of the crystal growth velocity of the phase-change material AgInSbTe, as derived from laser-based time-resolved reflectivity measurements. We observe a strict Arrhenius behaviour for the growth velocity over eight orders of magnitude (from ~10 nm s−1 to ~1 m s−1). This can be attributed to the formation of a glass at elevated temperatures because of rapid quenching of the melt. Further, the temperature dependence of the viscosity is derived, which reveals that the supercooled liquid phase must have an extremely high fragility (>100). Finally, the new experimental evidence leads to an interpretation, which comprehensively explains existing data from various different experiments reported in literature.
Highlights
Phase-change materials are the basis for next-generation memory devices and reconfigurable electronics, but fundamental understanding of the unconventional kinetics of their phase transitions has been hindered by challenges in the experimental quantification
AgInSbTe is chosen as material under investigation because it is successfully applied in data storage technologies and many relevant physical properties have been experimentally quantified for this alloy in the past
That other materials with high fragility, i.e. typically organic/ molecular compounds, generally show very slow crystallization kinetics because of their rather cumbersome building blocks that need to be rearranged, while the corresponding driving forces per unit are not so high. It seems that it is the unusual combination of low viscosity in the liquid, small building blocks and significant driving forces, together with an extremely high fragility that opens up a wide temperature window of low viscosity and high crystallization speeds
Summary
Phase-change materials are the basis for next-generation memory devices and reconfigurable electronics, but fundamental understanding of the unconventional kinetics of their phase transitions has been hindered by challenges in the experimental quantification. For instance, the study and production of silicon single crystals has been the basis of today’s semiconductor industry, mineral formation continues to be one of the most intriguing topics within earth sciences Among this wide variety of systems, the family of so-called phase-change materials represents a fascinating case, as crystallization can be observed here on a very small length scale of only a few nanometres and on an extremely short, that is, nanoseconds timescale[2,3]. Thanks to these unique switching properties, phasechange materials are already employed in high-density and ultrafast memories[4]. Fast measurements have always been performed in a non-isothermal way employing short laser or voltage pulses to crystallize a small volume of material causing severe difficulties to obtain the temperature dependence of nucleation and growth velocities[12,13,14,15]
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