DETECTION OF METALLIC IMPURITIES BY RESONANT IONIZATION SPECTROMETRY

A resonant ionization mass spectrometer has been developed for the det ection of trace amounts of metallic impurities in solids. This instrum ent is essentially a quadrupole SIMS in which the sputtered neutrals a re resonantly photoionized with a laser beam. The wavelength at which various metals can be ionized by using the simplest 1 + 1 photon schem e as well as the laser power required to saturate the ionization have been determined. Tile sensitivity of the method has been evaluated wit h calibrated samples containing known amounts of dopants, and, despite of the simple ionization scheme used, sub-ppma detection limits have been found. Finally the depth profiling capabilities of the instrument have been demonstrated.