Substrate effect on electronic sputtering yield in polycrystalline fluoride (LiF, CaF 2 and BaF 2) thin films

Abstract

Influence of substrate on electronic sputtering of fluoride (LiF, CaF 2 and BaF 2) thin films, 10 and 100 nm thin, under dense electronic excitation of 120 MeV Ag 25+ 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 × 10 6 atoms/ion for LiF film on glass substrate, than that is reported for bulk materials/crystals (∼10 4 atoms/ion), while a lower value of the yield (2.3 × 10 6 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.