Radiofrequency glow discharge-optical emission spectrometry for the analysis of metallurgical-grade silicon

The quantitative analysis of metallurgical- grade silicon by direct current (dc) and radiofrequency (rf) glow discharge - optical emission spectrometry (GD-OES) is investigated. This material is highly in demand today, being the source of raw silicon for industrial applications. Samples of different thickness, between 1.6 and 4 mm, were evaluated. To avoid instabilities, soft electrical conditions ( 600 V and 10 - 12 mA) had to be selected for dc-GD, thus achieving poor sensitivity. However, results showed a higher performance of the rf-GD for trace analysis. The effect of the sample thickness was also studied by rf-GD-OES: while for samples thinner than about 2 mm the behaviour was similar to that of conductors, for thicker samples the observed behaviour resembled that of an insulator. Finally, the quantitative analysis of aluminium, calcium, iron, titanium and boron has been successfully achieved by using a multi-matrix calibration approach. All in all, these results demonstrate that rf-GD-OES may be a useful technique for the rapid and convenient analysis of metallurgical- grade silicon in industry.