Silicon trace element characterization

Trace-Element Characterization of Silicon. In order to define "solar grade" silicon with sufficient precision to make the optimum economic choice among possible production processes, Davis et al. doped a series of silicon ingots with single transition metal impurities and produced curves relating normalized photovoltaic efficiency to the concentration of the contaminant (36). Establishing the x-axis of these curves was not entirely straightforward. As a contribution to this work, NBS measured concentrations of a number of dopants in these samples, with the detection limits found in Table I. An illustration of the difficulty faced in this work is that forty percent of the concentrations determined at NBS differed from the nominal concentration by a factor of two or more. 

Published information on characterization of seven different materials has been gathered from the literature to serve as a guide to the use of existing analytical techniques. These seven materials are copper, silicon, gallium arsenide, potassium chloride, zinc sulfide, anthracene, and trace element glasses. Collectively they represent an extremely broad spectrum of analytical problems and illustrate both strong and weak points in the application of the present state of the art of measurement of composition. 

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