Investigation of the effects of matrix modification on the atomisation of germanium in atomic-absorption spectrometry with electrothermal atomisation and its application to the determination of germanium in AIII BV semiconductor microsamples

Abstract

For the determination of trace amounts of germanium in A^IIIB^V semiconductor microsamples, thin layers, etc., methods using electrothermal AAS were developed. The atomisation processes were investigated in nitric acid, sulphuric acid, hydrobromic acid and alkaline media. It was found that matrix modification by some metal nitrates [the best results were obtained in the presence of Ni(NO₃)₂ and Ba(NO₃)₂] leads to a considerable improvement in the analytical sensitivity. The reason lies in the formation of thermally stable MGeO₃ compounds. The influence of nitrate ions is discussed. The strong depression of the Ge signal by sulphuric acid was clarified as being due to the formation of the thermally stable GeS molecules in the heated gas (plasma) of the graphite furnace. The prior evaporation of GeBr_x compounds can be avoided by using alkaline media.

The results were applied to the trace determination of germanium in some semiconductor materials. Analytical procedures and thin-layer separation methods involving a mechanical procedure or chemical etching are described. The detection limits lie in the parts per million range for sample amounts of less than 1 mg.