Molecular rearrangement and cluster formation in the secondary ion mass spectra (SIMS) of fluoride salts

Abstract

Secondary ion clusters with mass greater than 700 amu, e.g., K(KF) 12 + and up to 27 atoms, e.g., Na(NaF) 13 +, have been observed in the static SIMS spectra of MF (M = Li, Na, K), NaBF 4, and KPF 6. The long series of detected cluster ions of the type M(MF) n + indicates that there is a high degree of stability associated with these clusters. The observation of such clusters in the NaBF 4 and KPF 6 spectra suggest that there is significant molecular rearrangement occurring in the secondary ion emission process from such salts. The secondary ion Intensities provide a crude fit to the Saha-Eggert equation, yielding an electron temperature of ~12,000 K. The data are consistent with the plasma model of surface ionization in which rearrangement and cluster formation occur in the plasma.