This work refers to a process of purification of silica sand and, more particularly, to a process of iron and aluminium removal from the Algerian silica sand particles. Iron compounds are among the most difficult impurities to release from the sand particles. Several methods to remove iron from the sand particles are used; in our work we employed the acid leaching process as optimal solution to purify the silica sand. To this purpose, our work began by characterization of sand samples using X-ray fluorescence, for measurement of concentrations of major mineral oxides, and using atomic absorption, to determine the iron and aluminium concentrations in the silica sand particles. Through this study, the samples were enriched by acid leaching method, by removing the impurities from the crystal lattice, as well as from its surface. Thus reduction the impurities concentration increases, at the same time, the SiO₂ concentration. The obtained enriched silica can be used as raw material for silicon production, destined for photovoltaic application.
In this study we conducted thermal oxidation of Czochralski p-type <100> silicon wafers. The oxidation was carried out at temperatures in the range of 850-1000°C, in a gas mixture of N₂:O₂, in order to deposit a thin layer (10 nm) of thermal silicon dioxide (SiO₂), generally used in the surface passivation of solar cells. The measurements of effective minority carriers lifetime τ_{eff} using the quasi-steady-state photoconductance have shown degradation of different samples after oxidation process. The calculation of surface recombination velocity after the oxidation process at different temperatures, gave the same value of 40 cm s¯¹, showing a low surface recombination velocity and, therefore, a good surface passivation. Finally, a study based on sample illumination technique, allowed us to conclude that our samples are dominated by bulk Shockley-Read-Hall recombination, caused by Fe-related centers, thereby causing the degradation of the lifetime of minority carriers.
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