Electronic effects in low-energy ion sputtering of rare earth trifluorides

Abstract

Sputtering of CeF₃ and LaF₃ surfaces by singly charged rare gas ions (Ar⁺, He⁺, Xe⁺) with impact energies between 100 and 1500 eV has been performed. The emission of Ce⁺, La⁺ and F⁺ was measured by quadrupole mass spectrometer. The yield of Ce⁺, La⁺ decreases with decreasing impact energies; under ∼160 eV this decrease becomes very rapid compared with the decrease of F⁺ yield. For He⁺ bombardment a higher yield of F⁺ was observed than for Ar⁺ bombardment. The F⁺ yield for Xe⁺ bombardment is even lower than for Ar⁺. Therefore an electronic effect has to be assumed as a cause of the F⁺ emission enhancement as in the case of LiF. The quantitative differences between the data on LaF₃, CeF₃ and on LiF have been explained using our results on valence band measurements of rare earth trifluorides by XPS method.

Key Words:

• CeF₃
• LaF₃
• sputtering
• electronic effects