Micro-pulling-down
{{Short description|Crystal growth technique}}
{{Crystallization}}The micro-pulling-down (μ-PD) method is a crystal growth technique based on continuous transport of the melted substance through micro-channel(s) made in a crucible bottom. Continuous solidification of the melt is progressed on a liquid/solid interface positioned under the crucible. In a steady state, both the melt and the crystal are pulled-down with a constant (but generally different) velocity.
Many different types of crystal are grown by this technique, including Y3Al5O12, Si, Si-Ge, LiNbO3,
LiF, CaF2, BaF2, etc.{{cite book|title=Shaped Crystals: Growth by Micro-Pulling-Down Technique |editor=T. Fukuda |editor2=V.I. Chani |publisher=Springer-Verlag |location=Berlin |year=2007|isbn=978-3-540-71294-7|url=https://books.google.com/books?id=Dc6PJEOvRv8C|author1=Fukuda, Tsuguo|author2=Chani, Valery I}}{{cite journal |title=Challenge and study for developing of novel single crystalline optical materials using micro-pulling-down method |first=A. |last=Yoshikawa |author2=Nikl, M. |author3=Boulon, G. |author4= Fukuda, T. |journal=Opt. Mater. |volume=30 |year=2007 |issue=1 |pages=6–10 |doi=10.1016/j.optmat.2006.10.030|bibcode = 2007OptMa..30....6Y }}
Crystal growth routine
Standard routine procedure used in the growth of most of μ-PD crystals is well developed. The general stages of the growths include:{{Cite web |last=Kral |first=Robert |title=Development of micro-pulling-down method for growth of oxide and halide single crystals |url=https://dms.fzu.cz/25/pdfabstracts/13f.pdf |publisher=Institute of Physics CAS}}
- Charging of the crucible with starting materials (mixture of powders)
- Heating of the crucible until starting materials in the crucible are completely melted
- Upward displacement of the seed until its contact with the meniscus or crucible
- Formation of the meniscus and partial melting of the seed top
- Correction of the shape of the meniscus through appropriate adjustment of crucible temperature and position of the seed crystal
- Crystal growth through pulling of the seed in downward direction
- Separation of the as grown crystal from the meniscus
- Cooling of the system (including the crystal and the crucible) to room temperature