Measurements of energy distributions and yields of neutral Cu 2 and Cu 3 species sputtered from Cu by low energy Ar + ions

Abstract

Polycrystalline copper was bombarded by normally incident, very low energy argon ions ( E 0 = 100–1000 eV). The translational kinetic energy distributions and relative yields of neutral Cu 2 and Cu 3 species sputtered normally from the copper surface were measured using a secondary neutral mass spectrometer. The energy distribution of a given species (Cu 2 or Cu 3) was found to be approximately constant in shape for 600 < E 0 < 1000 eV. However, for E 0 < 600 eV, the distributions narrowed as the bomba ion energy was lowered. For a given bombarding ion energy, the energy distributions were found to be narrower for higher-order sputtered species, and the asymptotic falloff was steeper for the latter. The average kinetic energies ( E ) were in the order: E(Cu 1) > E(Cu 2) > E(Cu 3) . E(Cu 2) increased with increasing bombarding ion energy. The relat depend on the total sputtering yield of copper squared and the relative yield of Cu 3 on the total yield cubed. The measured polyatomic energy distributions and relative yields indicate that a multiple-collision process is responsible for sputtered neutral metallic cluster formation in this system.