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

Khalifa M, Hajji M, Ezzaouia H - Nanoscale Res Lett (2012)

Bottom Line: 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Laboratoire de Photovoltaïque, Centre des Recherches et des Technologies de l'Energie (CRTEn), Technopôle de Borj-Cédria BP 95, Hammam-Lif, 2050, Tunisia. mhajji2001@yahoo.fr.

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.

No MeSH data available.


Evolution of the concentration with the annealing temperature for impurities. Impurity concentration less than 25 ppm (a) and those with a concentration higher than 25 ppm (b).
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Figure 4: Evolution of the concentration with the annealing temperature for impurities. Impurity concentration less than 25 ppm (a) and those with a concentration higher than 25 ppm (b).

Mentions: After the discussion of porous silicon properties, we will focus our interest in this section to the study of its gettering effect when subjected to a photo-thermal annealing stage at different temperatures. Table 1 resumes the concentrations of different impurities present in silicon powder before and after purification steps. Depending on their concentrations obtained after the thermal annealing at 700°C, the impurities are divided into two groups: the first contains impurities with a concentration less than 25 ppm, and the second contains those with higher concentrations. The evolution of the concentration with the annealing temperature for two groups is presented in Figure 4a,b. Results show an important decrease in the impurity concentrations after the formation of a porous layer followed by thermal annealing. This reduction is as important as the annealing temperature is higher. After the thermal annealing at 900°C, about 99.991% of Fe, 99.03% of Al, 99.26% of Cr, and 98.24% of Mn were removed; and the purity of silicon powder increases from 99.1% (for the untreated powder) to about 99.995%.


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

Khalifa M, Hajji M, Ezzaouia H - Nanoscale Res Lett (2012)

Evolution of the concentration with the annealing temperature for impurities. Impurity concentration less than 25 ppm (a) and those with a concentration higher than 25 ppm (b).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3475061&req=5

Figure 4: Evolution of the concentration with the annealing temperature for impurities. Impurity concentration less than 25 ppm (a) and those with a concentration higher than 25 ppm (b).
Mentions: After the discussion of porous silicon properties, we will focus our interest in this section to the study of its gettering effect when subjected to a photo-thermal annealing stage at different temperatures. Table 1 resumes the concentrations of different impurities present in silicon powder before and after purification steps. Depending on their concentrations obtained after the thermal annealing at 700°C, the impurities are divided into two groups: the first contains impurities with a concentration less than 25 ppm, and the second contains those with higher concentrations. The evolution of the concentration with the annealing temperature for two groups is presented in Figure 4a,b. Results show an important decrease in the impurity concentrations after the formation of a porous layer followed by thermal annealing. This reduction is as important as the annealing temperature is higher. After the thermal annealing at 900°C, about 99.991% of Fe, 99.03% of Al, 99.26% of Cr, and 98.24% of Mn were removed; and the purity of silicon powder increases from 99.1% (for the untreated powder) to about 99.995%.

Bottom Line: 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Laboratoire de Photovoltaïque, Centre des Recherches et des Technologies de l'Energie (CRTEn), Technopôle de Borj-Cédria BP 95, Hammam-Lif, 2050, Tunisia. mhajji2001@yahoo.fr.

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.

No MeSH data available.