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Abstract Optoelectronics are crucial for developing energy‐efficient chip technology, with phase‐change materials (PCMs) emerging as promising candidates for reconfigurable components in photonic integrated circuits, such as nonvolatile phase shifters. Antimony sulfide (Sb2S3) stands out due to its low optical loss and considerable phase‐shifting properties, along with the non‐volatility of both phases. This study demonstrates that the crystallization kinetics of Sb2S3can be switched from growth‐driven to nucleation‐driven by altering the sample dimension from bulk to film. This tuning of the crystallization process is critical for optical switching applications requiring control over partial crystallization. Calorimetric measurements with heating rates spanning over six orders of magnitude, reveal that, unlike conventional PCMs that crystallize below the glass transition, Sb2S3exhibits a measurable glass transition prior to crystallization from the undercooled liquid (UCL) phase. The investigation of isothermal crystallization kinetics provides insights into nucleation rates and crystal growth velocities while confirming the shift to nucleation‐driven behavior at reduced film thicknesses—an essential aspect for effective device engineering. A fundamental difference in chemical bonding mechanisms was identified between Sb2S3, which exhibits covalent bonding in both material phases, and other PCMs, such as GeTe and Ge2Sb2Te5, which demonstrate pronounced bonding alterations upon crystallization.
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Decoupling Nucleation and Growth in Fast Crystallization of Phase Change Materials
Abstract Disentangling nucleation and growth in materials that crystallize on the nanosecond time scale is experimentally quite challenging since the relevant processes also take place on very small, i.e., sub‐micrometer length scales. Phase change materials are bad glass formers, which often crystallize rapidly. Here systematic changes in crystallization kinetics are shown in pseudo‐binary compounds of GeTe and Sb2Te3and related solids subjected to short laser pulses. Upon systematic changes in stoichiometry, the speed of crystallization changes by three orders of magnitude concomitantly with pronounced changes in stochasticity. Resolving individual grains with electron backscatter diffraction (EBSD) permits to disentangle of the process of nucleation and growth. From these experiments, supported by multiphysics simulations of crystallization, it can be concluded that high crystallization speeds with small stochasticity characterize phase change materials with fast nucleation, while compounds that nucleate slowly crystallize much more stochastically.
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- Award ID(s):
- 1832817
- PAR ID:
- 10641114
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Functional Materials
- Volume:
- 34
- Issue:
- 39
- ISSN:
- 1616-301X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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