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

本研究首次提出了一种新的提拉法，将超声波辐射到液浴中，从液浴中生长出单晶。这种新方法有效地利用了熔池中产生的超声波驻波，以抑制自然对流引起的热和溶液波动，并在抑制熔体过冷的情况下生长大晶体。总结如下：1.对熔体中自然对流的流型进行了分类，并用热Rayleigh数和溶质Rayleigh数之间的相互关系表示了流型。2.在等于波长一半的深度处存在共振液体深度。3.在此过程中应利用脱气熔体，以抑制干扰流体对流的有效控制的空化现象。4.利用阴影图法显示的流场和声场d…，研究了超声波对脱气水中自然对流的影响。更多的是用超声仪检测的。超声波在音速节点处约束被加热的部分流体，而在音速环路处限制冷却的流体部分。在水中产生的力的方向与假想的淹没在水中的流体颗粒所受辐射压力的方向一致，这种流体颗粒与周围的散体具有不同的声学性质，这取决于不同的密度和不同的声速。5.在超声能量密度增加的情况下，铝示踪法显示的流型表明，即使在均匀的温度场下，在声速回路附近也形成了流体适度循环的滞流区。这一区域被认为是由流体中周期性分布的辐射压力造成的。6.利用模拟CZ装置，研究了超声波对水中强迫对流、自然对流和混合对流的影响。在低能量密度下，超声波稳定了对流场，而在能量增加的情况下出现的滞流区甚至对包括强迫对流在内的流场也有很大的影响。较少

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