Abstract

Development of methods capable of quantitatively detecting low levels of impurities or dopants on surfaces is a formidable task. Instruments for this purpose must be extremely sensitive since the total number of surface atoms is quite low and yet must also be able to distinguish surface atoms from the much larger number of atoms in the bulk. Surface analysis by resonance ionization of sputtered atoms (SARISA) is a trace analysis technique which meets these criteria. Employing SARISA, determination of Fe and Ti concentrations on Si and Mo substrates has been performed. These experiments yield detection limits of 30 ppb with the removal of less than a monolayer of material. At present the detection limit of the SARISA apparatus is fixed by noise due to nonresonance ionization of other sputtered elements. This problem and other noise sources are discussed in light of the potential of SARISA to achieve sensitivities below 1 ppb.

© 1985 Optical Society of America