Emeritus Professor of Physics
My most recent research has addressed the problem of sputtering of metal surfaces by low energy ions. Ions incident upon a metal surface lead to the ejection of atoms, ions, excited atoms and ions, electrons, and photons from the surface. Analysis of data from the published literature and data obtained at Case Western Reserve University has revealed that the yields of these various sputter products per incident ion often have a surprisingly simple dependence on the energy of the incident ion. The yield, Y, as a function of incident ion energy, E, is given by
Y = A exp[ -B / (E + C) ],
where A, B, and C are constants determined by fitting the yield vs. energy data. The values of these fitted parameters depend on the particular combination of incident ion, target surface, and product particle. This relation between Y and E suggests a thermal model for the sputtering process with an effective temperature proportional to the energy of the incident ion. However, the microscopic details of such a model are unclear at the present time.