The effect of Ultrasonic Wave on Czochralski Process for Growing Single Crystal

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This study originally proposes a new Czoehralski process with radiating ultrasonic wave into liquid bath from which single crystal grows. This new method effectively utilizes ultrasonic standing wave established in the bath mainly so as to suppress thermal and solutal fluctuation induced by natural convection as well as to grow large crystal under suppressed supercooling of melt. Concluding remarks are as follows: 1. Flow regimes of natural convection in melt are classified and illustrated on a diagram as is specified by an interrelation between thermal and solutal Rayleigh numbers. 2. A resonant liquid depth exists at every depth equal to half of the wave length. 3. Degassed melt should be utilized in this process so as to suppress cavitation phenomena which interfere effective control of fluid convection. 4. The effect of ultrasonic wave on natural convection in degassed water is investigated on the basis of both the flow field visualized by a shadowgraph method and the sonic field d … More etected by an ultrasonic meter. Ultrasonic wave constrained a heated part of fluid at a sonic node whereas a cooled one at a sonic loop. The direction of force induced in water coincides with that of the radiation pressure acting on a hypothetically submerged fluid particle which has different acoustic properties from surrounding bulk depending on different density and different sonic velocity. 5. At increased density of ultrasonic energy, flow pattern visualized by the aluminum tracer method indicated that a stagnant area, in which moderate circulation of fluid occurs was formed nearby a sonic loop even at a uniform temperature field. This area is considered to be resulted from periodically distributed radiation pressure in fluid. 6. Using a simulated CZ device, the effect of ultrasonic wave on forced convection, natural convection and mixed convection in water has been investigated. At low density of ultrasonic energy, ultrasonic wave stabilizes the convection field whereas a stagnant area which emerges in increased energy case considerably changes even the flow field including forced convection. Less