ANALYSIS OF GAAS USING A COMBINED RF GLOW-DISCHARGE AND INDUCTIVELY-COUPLED PLASMA SOURCE-MASS SPECTROMETER

A radiofrequency (r.f.) glow discharge ion source was coupled to a dou ble-focusing sector field mass spectrometer with reverse Nier-Johnson geometry. The glow discharge cell powered by a 13.56 MHz generator was connected directly to the interface of the mass spectrometer. The r.f . glow discharge ion source operates optimally at an argon pressure of 2.5 hPa and radiofrequency powers of 30 W. With increasing argon pres sure more complex mass spectra were observed due to the higher molecul ar ion formation rate. The analytical performance of r.f. glow dischar ge mass spectrometry was investigated for the trace elemental analysis of semi-insulating gallium arsenide crystals. Using ICP-MS after matr ix separation for a better quantification of multielement determinatio n of trace impurities, detection limits comparable to r.f. GDMS in the low ng/g concentration range are obtained. (C) 1997 Elsevier Science B.V.