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The interface inversion process during the Czochralski growth of high melting point oxides

Authors
Journal
Journal of Crystal Growth
0022-0248
Publisher
Elsevier
Publication Date
Volume
265
Identifiers
DOI: 10.1016/j.jcrysgro.2004.02.087
Keywords
  • A1. Convection
  • A1. Heat Transfer
  • A1. Interfaces
  • A1. Marangoni Convection
  • A1. Thermocapillary Convection
  • A2. Czochralski Method

Abstract

Abstract High melting point oxides show an interface inversion from a convex interface shape to a flat or concave interface when grown after the Czochralski method with constant crystal rotation rate and increasing crystal radius (as in the shoulder region). Under the described conditions one observes during YAG-growth a sudden and uncontrollable interface change, called interface flip, at a certain critical crystal rotation rate. We describe model experiments and numerical simulations of this inversion process. We show that it is connected with a flow transition at a certain critical rotational Reynolds number Re c. This Re c increases with the convex interface deflection and with the strength of the buoyant-thermocapillary flow near the free melt surface towards the crystal. A self-amplifying process, involving the back-melting of the crystal cone, starts when Re c is reached. The dynamics of the back-melting is explained. A more vigerous interface inversion process is expected for systems with large interface deflections and for systems with smaller dynamic Bond number, e.g. smaller crucibles.

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