Fundamentals of Heterogeneous Nucleation with Application to the Optimization of Horizontal Ribbon Growth

该奖项支持对凝固动力学新模型的研究，并利用它们来优化水平带状生长（HRG）过程。HRG是一种生产用于太阳能电池的单晶硅薄晶片的技术，与目前使用的技术相比，它有可能显著降低生产成本（可能降低75%）。商业化尚未成功，主要是因为缺乏对凝固动力学的了解。新的模式能够预测在HRG实验中观察到的目前无法解释的现象。这些模型有可能影响HRG以外的晶体生长过程，从而导致蓝宝石或锗等硅以外材料的新应用。这项工作将为晶体生长的基本原理提供更深入的见解，并加速新的生长技术的发展，这将反过来帮助美国利用可再生资源实现能源独立，并在美国发展先进制造业。目前二维成核理论的推导是假设成核发生在一个面积无限的均匀环境中，这总是导致多核生长。然而，在所有现实的生长过程中，总是存在温度变化，限制了二维成核发生的区域。这些温度变化的影响将使用蒙特卡罗和分子动力学模拟进行研究，其结果将用于开发新的二维成核模型。该模型将预测二维成核和阶梯扩展在空间变化的温度场没有先验假设多核生长。该模型将被纳入HRG过程的高阶精确有限元模拟。这些连续体模拟将预测二维和三维流动和凝固不稳定性的开始及其对生长过程的影响。它们将用于优化工艺，以实现以高生产率生产均匀、薄的硅片。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This award supports research into new models of solidification kinetics and employs them to optimize the horizontal ribbon growth (HRG) process. HRG is a technique for producing thin wafers of single-crystal silicon for use in solar cells, which has the potential to significantly lower production costs (possibly 75% lower) compared to currently used techniques. Commercialization has not yet been successful mainly because of a lack of understanding of the solidification dynamics. New models enable the prediction of currently unexplained phenomena observed in HRG experiments. The models have the potential to impact crystal growth processes beyond HRG, leading to new applications with materials other than silicon such as sapphire or germanium. This work will provide deeper insights into the fundamentals of crystal growth and accelerate the development of new growth techniques, which will in turn help the US to achieve energy independence using renewable resources and grow advanced manufacturing in the US.Current theories for 2D Nucleation are derived assuming the nucleation occurs in a uniform environment with an infinite area, which always results in polynuclear growth. However, in all realistic growth processes, there are always temperature variations that limit the area where 2D nucleation will occur. The effect of these temperature variations will be investigated using Monte Carlo and Molecular Dynamic simulations, the results of which will be used to develop a new 2D nucleation model. This model will predict 2D nucleation and step propagation in spatially varying temperature fields without a-priori assuming polynuclear growth. This model will be incorporated into high-order accurate finite element simulations of the HRG process. These continuum simulations will predict the onset of 2D and 3D flow and solidification instabilities and their impact on the growth process. They will be used to optimize the process to enable the production of uniform, thin silicon wafers, at a high production rate.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.