Features of Impurity Segregation and Microstructure of Si Ingots obtained by Electron-Beam Purification of Metallurgical Grade Silicon

Authors V.O. Osokin1 , Ya.A. Stel’makh1 , Yu.A. Kurapov1 , P.O. Shpak2

1Paton Institute for Electric Welding, NASU, 11, Kazimir Malevich St., 03150 Kyiv Ukraine

2Institute for Carbon Nanomaterials, Ltd., office 110, build. 2, Khmelnitske St., 21036 Vinnitsa, Ukraine

Е-mail kist2002@ukr.net
Issue Volume 14, Year 2022, Number 6
Dates Received 29 October 2022; revised manuscript received 22 December 2022; published online 27 December 2022
Citation V.O. Osokin, Ya.A. Stel’makh, et al., J. Nano- Electron. Phys. 14 No 6, 06012 (2022)
DOI https://doi.org/10.21272/jnep.14(6).06012
PACS Number(s) 81.20, 64.75.Qr
Keywords Purification, Structure (104) , Impurities, Segregation, Coagulation, Upgraded metallurgical grade silicon, Electron-beam Melting.

Today, solar-grade silicon (SG-Si) is the most used material for the manufacture of solar photovoltaic converters (SPVC), which are widely used in the renewable energy, industry and households. Improving the efficiency of SPVC while reducing the cost of production and strengthening environmental requirements is the urgent and important task for modern applied science and technology development. The solution to solving this problem is due, among other things, to refining methods: vacuum purification (VP) and oxidative purification (OP) during electron-beam melting (EBM) of metallurgical-grade silicon (MG-Si). The influence of VP and OP on the microstructure of silicon ingots, obtained by the EBM of MG-Si, is studied in the present paper. It is experimentally established that the structure of ingots does not depend on the type of VP/OP refining used during EBM and is determined prefer by the technological/thermo-physical conditions of their solidification/crystallization. The structure of the obtained ingots consists mainly of more frequent crystallites, their main axis is perpendicular to the surface of solidification. In the obtained ingots of upgraded metallurgical silicon (UMG-Si) by EBM, there is a noticeable segregation of inclusions with an increase in their number in the direction from the center to the free surface of the melt that solidified last. The sensitivity of the particle sizes of inclusions according to the type of refining of metallurgical silicon VP/OP is noted, in contrast to the size of crystallites. The absence of segregation of impurities onto grain boundaries, regardless of the selected refining method (VP/OP), is confirmed in ingots of UMG-Si obtained by EBM of MG-Si. Analysis of the chemical composition of impurities in the obtained ingots confirms the presence of the "heredity effect" – majors of impurities are autonomous single-element phases of residual and low-component impurities with a ratio of elements of their chemical composition similar to those in the initial MG-Si.

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