Development of resonance‐enhanced multiphoton ionization SNMS for state‐selective detection of sputtered atoms under low‐energy ion irradiation

Abstract

AbstractAn instrument for a sputtered neutral mass spectrometry with a quadrupole mass spectrometer (QMS) by resonance‐enhanced multiphton ionization method is developed to study sputtered neutrals emission phenomena under ion irradiation in a low‐energy region. We have prepared a pulsed primary ion beam and an ion counting system, and have optimized the operation parameter including a sample bias, energy analyzer voltages, pulsed timing of laser and ion beam, etc.A yield ratio of the lowest‐lying excited state a5S2 to the ground state a7S3 for sputtered Cr atoms has been measured as a function of incident energy of Ar+ and O2+ down to 600 eV using a polycrystalline Cr sample. The yield ratio has become a constant value for the Ar+ incidence, while it has exponentially increased below 1 keV for the O2+ incidence. It is found that the internal energy distribution of sputtered Cr atoms has been significantly influenced by oxygen density at the surface. Copyright © 2011 John Wiley & Sons, Ltd.