Sputtering Yield of Germanium in Rare Gases

Abstract

Sputtering yields of germanium bombarded by Xe⁺, Kr⁺, A⁺, Ne⁺, and He⁺‐ions under normal incidence at energies up to 400 ev have been determined. Yield vs ion energy curves consist of three parts; (1) a low‐energy tail (possibly caused by a process of stepwise sputtering), (2) a region in which yield rises proportionally with ion energy, and above ion velocities of ∼3×10⁶ cm/sec, (3) a region in which the yield rises less than proportionally with ion energy. The slope in the proportional region is largely determined by the energy transfer factor, η=4m₁m₂/ (m₁+m₂)². Surprisingly, the ``cut in'' energies do not follow V₀∼H/η (H=heat of sublimation) but are found to be much lower than expected for the lighter gases. The empirical result, V₀∼H(m₁)^½/η (m₁=atomic weight of ion), is not yet understood.