Abstract There are always undesired grains formed at the beginning of unseeded THM growth which deteriorate the crystal quality greatly. In this paper, several ingots with the diameter of 27 mm were grown by unseeded THM to investigate the nucleation process. The growth temperature in the experiments was 750 °C and the growth rate was 5 mm/day. The influence of crucible bottom geometry and temperature gradient on nucleation are studied. Numerical simulations of thermal and concentration fields were also performed for the THM process to study the growth process. The simulation results show that square cavity flow's structure and parabolic wall temperature profile are the main reason for secondary nucleation in the radial direction. Dummy crystal with cold finger was introduced in order to stabilize the thermal field and modify the lateral temperature gradient. Subsequent experimental results indicate that a large longitudinal temperature gradient with small lateral temperature gradient is more favor to suppress secondary nucleation and maintain stable growth.

中文翻译：

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在 CdZnTe 晶体的非晶种 THM 生长过程中控制成核

摘要 在无晶种的THM生长开始时，总会有不希望有的晶粒形成，大大降低了晶体质量。在本文中，通过未接种的 THM 生长了几个直径为 27 mm 的锭，以研究成核过程。实验中生长温度为 750 ℃，生长速度为 5 mm/天。研究了坩埚底部几何形状和温度梯度对成核的影响。还对 THM 过程进行了热场和浓度场的数值模拟，以研究生长过程。模拟结果表明，方腔流动的结构和抛物线壁温剖面是径向二次形核的主要原因。为了稳定热场和修改横向温度梯度，引入了带有冷手指的虚拟晶体。随后的实验结果表明，较大的纵向温度梯度和较小的横向温度梯度更有利于抑制二次成核并保持稳定生长。