Silicon and indium as secondary cathodes for the analysis of solid alumina and sapphire by slow-flow direct-current glow discharge mass spectrometry

We demonstrate and compare the capabilities of indium and silicon as secondary cathodes for the analysis of flat, solid alumina and sapphire matrices by direct current glow discharge mass spectrometry (dc-GDMS). The mask designs and the glow discharge conditions are optimised for signal ratio and absolute intensity. The mask material was found to be a small factor in matrix to mask ratio and signal intensity despite the large difference in properties between indium and silicon. The results indicate that the discharge conditions play the most significant role. The mask material did not appear to affect the RSFs. On sapphire with indium, the possible discharge conditions and performance were limited due to a collapse of discharge. This was not the case for silicon, which proves to be a good alternative as secondary cathode material.