Purification of silicon powder by the formation of thin porous layer followed byphoto-thermal annealing

Marouan Khalifa,Hatem Ezzaouia,Messaoud Hajji

doi:10.1186/1556-276x-7-444

Abstract

Porous silicon has been prepared using a vapor-etching based technique on a commercial silicon powder. Strong visible emission was observed in all samples. Obtained silicon powder with a thin porous layer at the surface was subjected to a photo-thermal annealing at different temperatures under oxygen atmosphere followed by a chemical treatment. Inductively coupled plasma atomic emission spectrometry results indicate that silicon purity is improved from 99.1% to 99.994% after annealing at 900°C.

Highlights

Porous silicon (PSi) is a nano-structured material that can be obtained by electrochemical [1], stain etching [2,3], or vapor phase etching of silicon wafers [4,5]
We present the possibility of gettering impurities from commercial silicon powder (SPw) by photothermal annealing in oxygen atmosphere using a thin porous silicon layer on the surface of silicon grains
The silicon powder with thin porous silicon layer is subjected to a photo-thermal annealing stage under oxygen atmosphere in the aim to remove the unwanted impurities

Summary

Background

Porous silicon (PSi) is a nano-structured material that can be obtained by electrochemical [1], stain etching [2,3], or vapor phase etching of silicon wafers [4,5]. The main advantages of stain etching and vapor etching methods, if compared with electrochemical one, are their simplicity and capability to produce large area porous silicon layers. Porous silicon elaborated by different methods is extensively used in photovoltaic applications as an antireflection coating or as a gettering layer due to its large specific surface and chemical reactivity. Gettering of impurities by the formation of a thin porous silicon layer followed by a thermal annealing in a nitrogen, oxygen, or SiCl4 atmosphere has been used [6,7]. We present the possibility of gettering impurities from commercial silicon powder (SPw) by photothermal annealing in oxygen atmosphere using a thin porous silicon layer on the surface of silicon grains.

Methods

Results and discussions

Conclusion