Evidence against Focused Chains in High-Yield Copper Sputtering

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Abstract
The yield (atoms/ion) and angular distribution (atoms/ion sr) of monocrystalline copper sputtered by 1- to 10-keV cesium ions has been measured as a function of target temperature at normal and at 45° incidence to the (100) face. The yield as a function of energy and at normal incidence attained a broad maximum of 6.2 atoms/ion in the neighborhood of 5 keV and was independent of target temperature variation from 77 to 493°K. At non-normal incidence, the sputtering yield was markedly affected by the opacity of the target lattice to the incident ion beam, as is demonstrated by a higher yield for incidence along the [755] direction when compared with the [110] direction. The fitting of an analytic function to the extensive angular emission data by nonlinear regression analysis indicated that preferred emission along the closepacked direction was of secondary importance, decreasing from 18% at 1 keV to 10% at 10 keV. The primary contribution to the sputtering distribution followed a polar angle cosine dependence.