THE INVESTIGATION OF INSTRUMENTAL AND SAMPLE PARAMETERS AS POTENTIALS SOURCES FOR AFFECTING THE REPRODUCIBILITY OF ISOTOPIC RATIO MEASUREMENTS IN SECONDARY-ION MASS-SPECTROMETRY

In this study a number of instrumental and sample parameters were investigated as potential sources for affecting the reproducibility of isotopic ratio measurements in secondary ion mass spectrometry. The study consisted of examining the energy distributions of the individual isotopes using different parameter settings. This way, 70% of the observed isotopic variation could be ascribed to the setting of certain instrumental parameters such as the field aperture, the contrast diaphragm and the energy window width. In addition, the effects of differing crystal orientations in the sample and macroscopic surface characteristics upon the reproducibility were evaluated using imaging techniques.