An empirical formula for E-z in the modified Sigmund formula for low energy heavy ion bombardment

摘要

Based on Yamamura's theory, Zhang took the natural boundary condition into account and proposed the modified Sigmund's formula which agrees well with the experimental results of the sputtering yield and the energy distributions of sputtered atoms. While, the new parameter E-z introduced by Zhang is still unclear. This work mainly studies the experimental results when Ar, Kr and Xe bombard different targets to obtain the best fitted E-z, and proposes an empirical formula of it. Two factors that may impact on E-z are discussed: mass ratio and the correction factor of electronic stopping 'Psi'. Putting Psi into the periodic table, we found that the values of psi in the same congeners are similar and have the trend of 'W' shape. The row number (n) and column number (m) of the elements in the periodic table are used to fit the 'W' shape. The parabolic model is used to approximate the sputtering yield when E < E-z. Finally, the sputtering yield and the energy distributions of some common elements are used to verify the calculation method of E-z. The results show that the obtained formula can be applied to the situation of low energy heavy ion sputtering and to supplement Zhang's model. (C) 2016 Elsevier Ltd. All rights reserved.