Determination of impurities in solar grade silicon by inductively coupled plasma sector field mass spectrometry (ICP-SFMS) subsequent to matrix evaporation
A method for the determination of 22 trace impurities in solar grade silicon after dissolution in a mixture of HF and HNO3 and subsequent matrix evaporation is reported. The presented method involves a simple, inexpensive, one-vessel sample preparation apparatus design. The recoveries of B, Na, Mg, Al, P, K, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Mo, Sb, W, and Tl at 250 mg kg−1 level are in the range of 93 to 108%. After careful selection of monitored isotopes and their respective resolutions, a sector field mass spectrometer has been used to carry out the measurements. Limits of determination down to 120 ng kg−1 have been obtained using a calibration by three-point standard addition. The method was tested on diluted NIST SRM 57b silicon powder as well as on synthetic test samples and also applied successfully on raw solar grade silicon samples in an interlaboratory comparison including NAA.