Substrate effect on electronic sputtering yield in polycrystalline fluoride (LiF, CaF2 and BaF2) thin films

Influence of substrate on electronic sputtering of fluoride (LiF, CaF2 and BaF2) thin films, 10 and 100 nm thin, under dense electronic excitation of 120 MeV Ag25+ ions irradiation is investigated. The sputtering yield of the films deposited on insulating (glass) and semiconducting (Si) substrates are determined by elastic recoil detection analysis technique. Results revealed that sputtering yield is higher, up to 7.4 × 106 atoms/ion for LiF film on glass substrate, than that is reported for bulk materials/crystals (∼104 atoms/ion), while a lower value of the yield (2.3 × 106 atoms/ion) is observed for film deposited on Si substrate. The increase in the yield for thin films as compared to bulk material is a combined effect of the insulator substrate used for deposition and reduced film dimension. The results are explained in the framework of thermal spike model along with substrate and size effects in thin films. It is also observed that the material with higher band gap showed higher sputtering yield.