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Presolidification in Eutectic Droplets.
Bene Poelsema1, Zhiguo Zhang1, Harold J W Zandvliet1
1Physics of Interfaces and Nanomaterials, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, Netherlands.
Physical Review Letters
|September 22, 2023
Summary
Presolidification, the opposite of premelting, influences the movement of germanium-platinum (Ge-Pt) droplets. Droplet motion direction unexpectedly shifts to align with the substrate
Area of Science:
- Materials Science
- Surface Science
- Physics
Background:
- Premelting describes surface disordering of solids at temperatures below melting.
- Presolidification is the analogous phenomenon occurring at the liquid-solid interface, influencing material behavior.
- Understanding interface phenomena is crucial for controlling material properties and processes.
Purpose of the Study:
- To investigate the phenomenon of presolidification in eutectic Germanium-Platinum (Ge-Pt) droplets on a Germanium (Ge) substrate.
- To determine the influence of presolidification on the thermal gradient driven motion of these droplets.
- To explore the relationship between droplet morphology and motion direction.
Main Methods:
- Utilizing a substrate of Germanium (Ge) with a (110) surface orientation.
- Observing the behavior of micron-sized eutectic Ge-Pt droplets under controlled thermal gradients.
- Analyzing droplet motion direction and shape changes at temperatures near and above the eutectic temperature (T_C).
Main Results:
- At temperatures well above T_C, droplets moved towards the heat source regardless of substrate orientation.
- A distinct transition occurred at 90 K above T_C, with droplets exhibiting a strong preference for motion along the [001] azimuth.
- This directional motion was accompanied by a change in droplet shape from compact to elongated along the [001] direction.
- The observed behavior was attributed to presolidification effects at the liquid-solid interface.
Conclusions:
- Presolidification significantly impacts the directional motion of eutectic Ge-Pt droplets on Ge(110) substrates.
- The phenomenon dictates a transition in droplet movement from thermophilic to anisotropic motion.
- This finding provides new insights into interfacial phenomena and their role in material transport.
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