Recoil implantation from a thin source: I. Underlying theory and numerical results

Recoil implantation from a monolayer source, for example an adsorbed layer or a layer of altered stoichiometry, is considered. We introduce the incident ion current I, the fractional surface coverage characterizing the recoil source θ, the differential scattering cross-section dσ, and the integral distribution function F(x, ψ) for recoil-source atoms entering the target at angle ψ and stopping beyond x. The number of atoms implanted beyond x follows as $\text{H(x) = IθλN? σ F(x,ψ)}$. The receding of the target surface at velocity υ due to sputtering can be allowed for by integrating over $\text{x: H(x, t) = (}\text{1}\text{υ}\text{) ∫ H(x′)dx′}$. For very high doses the result is a steady-state situation in which the number of implanted atoms is given by H(x, ∞). Numerical results of four kinds are presented: H(x, H(x, ∞), the half-time for the build-up of the steady-state situation, and the half-depth of the implanted atoms, in all cases for oxygen on the surface of Be, Al, Mo and W.