Physical sputtering threshold

For Be and W, experimental data and the fit for the sputtering yield at normal incidence are shown in Fig. 9.f for D ions as a function of incident particle energy. Physical sputtering data are available for both materials from energies close to the threshold energy (9eV for D on Be and 200 eV for D on... 

The threshold energy is substantially lower than for physical sputtering. 

The reactive species can also be produced directly on the surface by ion- or electron-impact induced fragmentation of the physisorbed molecules of the reactant B (eq. 44). An example of this kind is the etching of Si, Si02 and other materials by XeFj upon bombardment of the surface by Ar ions or electrons. Alternatively, the molecular ion B, can dissociate upon collision with the surface and, subsequently, undergo chemical reaction. This kind of processes have been reviewed recently by Winters At ion energies above the threshold value for sputtering the situation is more complex and physical and chemical sputtering usually dominates. 

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