Influence of grain size on electronic sputtering of LiF thin films

The electronic sputtering from LiF thin films is investigated using 120 MeV Ag25+ ions in equilibrium charge state as projectiles. The sputter yield of Li and F from 160 nm thin polycrystalline LiF films with different grain sizes (22–58 nm) is measured with online elastic recoil detection analysis technique. The grain size of the films is estimated by glancing angle X-ray diffraction. The sputtering yield is of the order of 104 atoms/ion. A reduction in sputter yield is observed with increasing grain size. The results are discussed in terms of grain size effect along with thermal spike model. The electrons liberated in different directions from the ion track have different diffusion length according to its energy. The motion of the electrons is affected by the smaller grain size due to grain boundary scattering resulting in reduction in the mean diffusion length of the electrons, which finally enhanced energy deposition inside the grains and thus the sputter yield.