Spark source mass spectrometry of silicon for solar cells

Abstract

Spark source mass spectrometry (SSMS) is used to analyze metallurgical grade silicon powder which has been submitted to different purification steps. The principal advantage of this method in comparison to other analytical methods is the broad range of impurity elements detected simultaneously in each analysis. The silicon powder is mixed with gallium in a weight-ratio of 5∶1 and pressed in a moulding die to solid rods. Detection limits are in the range of 0.02–1 ppma with the exception of some few elements contained in the gallium or introduced during sample preparation. By using self-prepared standards relative sensitivity factors for 35 impurity elements have been determined to enhance the accuracy of the results. Concentration values for most elements are expected to be accurate within a factor of 2. As an example the results of SSMS-measurements referring to one special purification step (acid-treatment) are shown.