Ion Implantation and Synthesis of Materials - Studium

12.2 Sputtering of Single-Element Targets 161(a)Y2.001.501.00++++ +ArSi+0.051 2 5 10 20 50 100 200 500E (keV)(b)5.0045 keV Ions+Silicon++Y2.001.00++ +0.05+Sigmund (Theory)0 10 20 30 40 50 60 70 80Z 1Fig. 12.2. (a) Energy dependence of the Ar sputtering yield of Si and (b) incident iondependence of the Si sputtering yield. The solid line represents the calculations of Sigmund.The data in solid circles is from Andersen and Bay (1981), and the plus signs (+) representSRIM Monte Carlo simulations (Ziegler et al. 1985)where N is the atomic density of target atoms, S n (E 0 ) is the nuclear stopping crosssectionat energy E 0 , and NS n (E 0 ) = dE 0 /dx| n is the nuclear energy loss rate atenergy E 0 . The energy-dependent nuclear stopping cross section can be mostaccurately calculated using the ZBL nuclear stopping cross section given by(5.13). In (12.3), α is a correction factor, which is a function of M 2 /M 1 and rangesbetween 0.2 and 1.4, as shown in Fig. 12.3a. The value of α also increases withthe angle of incidence because of increased energy deposition near the surface,Fig. 12.3b.The material factor Λ in (12.2) contains the material parameters and is adescription of the number of recoil atoms that can escape from the solid. InSigmund’s description (1981)0−1Λ ≅4.2 / NU (nmeV )(12.4)