Simultaneous TOF spectra of sputtered and scattered neutrals and ions from 3 keV Ne+, Ar+, and Ar2+ bombardment of CsBr

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Abstract
A spectrometer system for simultaneous mass and velocity analysis of scattered and sputtered ions and velocity analysis of fast neutrals ejected from a surface by bombardment with a pulsed ion beam is described. Combination secondary ion and scattered neutral plus ion TOF spectra and their corresponding energy spectra for 3 keV Ar+ and Ar2+ bombardment of CsBr are presented. Selective sputtering of Br down to a steady state level is observed with Ne+ bombardment with an estimated depletion cross section of 10 Å2. Scattering spectra of neutrals plus ions and neutrals alone allow determination of scattered Ar+ ion survival fractions of 0.22 and 0.13 from 3 keV Ar+ collisions with Cs and Br, respectively. This indicates preferential neutralization during scattering from Br. Ion fractions for Ar2+ and Ar+ are determined for Ar2+ scattering, illustrating the stepwise neutralization process for multiply charged ions. With 3 keV Ar2+ bombardment the fractions surviving as Ar+ for Cs and Br collisions are 0.18 and 0.08, respectively, while the fraction surviving as Ar2+ is ∼0.10 for both atomic collisions. The ion fraction data are interpreted in terms of Auger and resonant neutralization transitions between the ion and specific surface atoms.