NSF Award
2317674
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.<br/><br/>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.<br/><br/>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.
