Role of marangoni tension effects on the melt convection in directional solidification process for multi-crystalline silicon ingots

• Published in: Journal of crystal growth Vol. 346; no. 1; pp. 40 - 44
• Main Authors: Li, Zaoyang, Liu, Lijun, Nan, Xiaohong, Kakimoto, Koichi
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.05.2012; Elsevier
• Subjects: A1. Computer simulation; A1. Directional solidification; A1. Marangoni tension; A1. Melt convection; Applied sciences; Argon; B3. Solar cells; Convection; Cross-disciplinary physics: materials science; rheology; Directional solidification; Energy; Exact sciences and technology; Flow rate; Growth from melts; zone melting and refining; Ingots; Materials science; Melts; Methods of crystal growth; physics of crystal growth; Natural energy; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Photovoltaic conversion; Physics; Shear stress; Silicon; Solar cells. Photoelectrochemical cells; Solar energy; Solidification; A1. Computer simulation; A1. Directional solidification; B3. Solar cells; A1. Marangoni tension; A1. Melt convection; Solar cells; Fluid mechanics; A1 Marangoni tension; Calcium selenides; A1 Computer simulation; A1 Directional solidification; Directional solidification; Digital simulation; Crucibles; Flow pattern; Computerized simulation; B3 Solar cells; Marangoni effect; A1 Melt convection; Shear stress; Stress effects; Silicon; Crystal growth from melts
• DOI: 10.1016/j.jcrysgro.2012.02.031
• ISSN: 0022-0248

We carried out global simulations to investigate the marangoni tension effect on the thermal and flow fields in the silicon melt of the directional solidification process for multi-crystalline silicon ingots. The argon flow rate was varied to provide different solidification conditions and to change the relative values between the argon shear stress and the marangoni tension at the melt free surface. We found that the marangoni tension together with the shear stress mainly influences the upper layer melt convection while the thermal buoyancy force dominates the bulk flow of the melt. At low argon flow rates, the argon shear stress can be neglected and the marangoni tension alone enhances the melt convection intensity near the gas–melt–crucible triple junction point. The marangoni tension is so weak that it cannot modify the melt flow pattern in this case. For medium flow rate, the marangoni tension can significantly weaken the shear stress effect at the outer part of the melt free surface, leading to a distinctive flow pattern in the silicon melt. With further increase in argon flow rate, the shear stress sharply increases and dominates the upper layer melt flow, limiting the marangoni tension effect to the triple point. The numerical results are helpful for better understanding and controlling of the directional solidification process for high quality multi-crystalline silicon ingots. ► Numerically investigated the Ma tension effects on the melt convection. ► Ma tension affects the melt convection at the outer part of the melt surface. ► Ma tension induces distinctive melt flow pattern at medium argon flow rate. ► Ma tension effect is limited to the triple point at large argon flow rate. ► Ma tension should be incorporated in accurate simulations of DS processes.