Model for the emission of quasi-thermal atoms during sputtering of metals in the nonlinear collision cascade regime

The ion sputtering of metals and frozen inert gases in the nonlinear collision cascade regime, where the density of the energy released in the bulk of the thermal peak exceeds the critical medium temperature, initiates the emission of quasi-thermal atoms. The energy spectrum of such atoms is substantially shifted toward low energies and is not described by a Maxwellian distribution. A simple emission model is proposed on the assumption of collisional motion of sputtered atoms in their flight from a target, and this model is used to derive an analytical formula for the calculation of the energy spectra of quasi-thermal atoms. A comparison of the calculated energy spectra of indium, krypton, and xenon atoms and the spectra measured during ion sputtering of indium and frozen inert gases in the nonlinear collision cascade regime shows their agreement at reasonable values of fitting parameters.