X-ray Based in Situ Investigation of Silicon Growth Mechanism Dynamics—Application to Grain and Defect Formation

• Published in: Crystals (Basel) Vol. 10; no. 7; p. 555
• Main Authors: Ouaddah, Hadjer, Becker, Maike, Riberi-Béridot, Thècle, Tsoutsouva, Maria, Stamelou, Vasiliki, Regula, Gabrielle, Reinhart, Guillaume, Périchaud, Isabelle, Guittonneau, Fabrice, Barrallier, Laurent, Valade, Jean-Paul, Rack, Alexander, Boller, Elodie, Baruchel, José, Mangelinck-Noël, Nathalie
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.07.2020; MDPI
• Subjects: Chemical Sciences; Cooling; Crystal defects; Crystal structure; Defects; Directional solidification; Dynamic structural analysis; Experiments; Grain boundaries; Grain structure; grains; growth; High temperature; Imaging techniques; Ingots; Material chemistry; Methods; Morphology; Nucleation; Particle beams; Photovoltaic cells; Radiography; Seeds; Silicon; Silicon wafers; Solar cells; Solidification; strain; Synchrotron radiation; Topography; Twinning; twins; X ray imagery; X-ray radiography; X-ray radiography and topography; Grains; Growth; Silicon; Bragg diffraction imaging; Twins; Strain; Dislocation
• DOI: 10.3390/cryst10070555
• ISSN: 2073-4352

To control the final grain structure and the density of structural crystalline defects in silicon (Si) ingots is still a main issue for Si used in photovoltaic solar cells. It concerns both innovative and conventional fabrication processes. Due to the dynamic essence of the phenomena and to the coupling of mechanisms at different scales, the post-mortem study of the solidified ingots gives limited results. In the past years, we developed an original system named GaTSBI for Growth at high Temperature observed by Synchrotron Beam Imaging, to investigate in situ the mechanisms involved during solidification. X-ray radiography and X-ray Bragg diffraction imaging (topography) are combined and implemented together with the running of a high temperature (up to 2073 K) solidification furnace. The experiments are conducted at the European Synchrotron Radiation Facility (ESRF). Both imaging techniques provide in situ and real time information during growth on the morphology and kinetics of the solid/liquid (S/L) interface, as well as on the deformation of the crystal structure and on the dynamics of structural defects including dislocations. Essential features of twinning, grain nucleation, competition, strain building, and dislocations during Si solidification are characterized and allow a deeper understanding of the fundamental mechanisms of its growth.