Sputtering with polyatomic ions: revisiting kinetic energy distributions of secondary ions

Abstract

A new more accurate data processing procedure for calibration of kinetic energies of secondary ions measured in magnetic sector secondary ion mass spectrometers has been developed. The procedure was applied to reprocessing of raw data from previously published measurements of kinetic energy spectra of secondary atomic and cluster ions sputtered from Ta by 6 keV/atom Au −, Au 2 − and Au 3 − projectiles. Absolute energies of the sputtered Ta n + ions were determined more accurately, which permitted a fairer comparison of energy spectra for the same secondary ions measured under bombardment with different primary ions. Most probable and mean energies were determined for the sputtered ions, and their energy spectra were converted into distributions over inverse velocities. The reprocessed experimental results revealed strong differences between results for atomic and diatomic ions and those for larger cluster ions (consisting of more than seven atoms). In particular, the comparison of atomic and polyatomic bombardment showed that there are strong differences between atomic and diatomic sputtered species, while there were almost no changes between larger sputtered clusters. Results are discussed in terms of observed enhancements under polyatomic ion bombardment for the total sputtering efficiency and the ionization of sputtered species.