Abstract

The conditions of detached solidification under controlled pressure differential across the meniscus were investigated. Uncoated and graphite- or BN-coated silica and pBN crucibles were used. Detached and partly detached growth was achieved in pBN and BN-coated crucibles, respectively. The results of the experiments are discussed based on the theory of Duffar et al.

Keywords: A2. Bridgman technique; A3. Detached growth; B1. Germanium

PACS: 81.05.Cy; 81.10.Fq

Article Outline

1. Introduction

2. Experimental procedure

3. Theoretical

4. Results and discussion

5. Summary

Acknowledgements

References

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Fig. 1. Experimental system: (a) growth configuration; (b) ampoule with silica crucible; (c) ampoule with pBN insert.

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Fig. 2. Schematic diagram of detached solidification.

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Fig. 3. Gap width as a function of meniscus pressure differential for (Θ+α)<180°.

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Fig. 4. Meniscus shapes for (Θ+α)<180°.

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Fig. 5. Crystals grown in pBN sleeves, their surface profiles, and the pressure differentials during growth. The dashed lines give the approximate position of the crucible wall.

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Fig. 6. Surface profile inside the pBN sleeve.

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Fig. 7. Gap width as a function of meniscus pressure differential for (Θ+α)>180°.

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Fig. 8. Meniscus shapes for (Θ+α)>180°.

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Fig. 9. Crystal grown in BN-coated silica crucible, its surface profile, and the pressure differentail during growth.

Table 1.
Attachment/detachment conditions

Crucible surface	Pressure differential, ΔP [mBar]	Gap width [μm]	Status
pBN	< −(40 to 50)	0	Attached
	−(30 to 40 to a few)	up to 15	Detached
BN coating	−(15 to 1)	0; 10–60	Mostly detacheda
	0 to 45	0	Attached
Silica	A negative few to 0	0; up to 60	Occasionally partly detached
Graphitized	0–30	0	Attached

^a Observed only when the ingot was melted along its entire length.

References

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[20] A. Cröll, unpublished results.

Corresponding author. NASA/Marshall Space Flight Center, XD42, Huntsville, AL 35812, USA. Tel.: +1 256 544 1272; fax: +1 256 544 8762.