THE EMISSION OF SECONDARY CLUSTERS AND ITS RELEVANCE FOR ANALYTICAL LASER-SNMS

The emission of secondary dimers and trimers under 8 keV Ar+ ion bombardment has been investigated under the aspects of its relevance for quantitative SNMS analysis and its implication for the basic understanding of the sputtering process. The measurements have been performed with a newly developed Laser-Multiphoton-Ionization-TOF-SNMS apparatus. The problematic of saturation and fragmentation of multimers in Laser-SNMS is addressed and compared for different ionization techniques. Cu and Cr metal as well as a CuAgAu alloy with known element concentrations have been investigated using 308 and 193 nm laser radiation for post-ionization. The data imply, that for these materials and primary ion energies dimer/atoms ratios of 10-30% are characteristic. These numbers also imply, that neglecting cluster-contributions can lead to substantial errors in quantitative analysis.