Diffusion in ion-implanted solids with non-uniform diffusion parameters

Abstract

Abstract There is increasing evidence that diffusion phenomena in ion-implanted solids do not follow normal diffusion kinetics at high doses. For example, diffusion profiles are sometimes found to move towards the surface with increasing temperature, while the diffusion temperature widths tend to be up to a factor-of-3 too narrow. Such results can be self-consistently explained by recognizing that the diffusion detrapping energy will ordinarily be greater in the vicinity of the damage mean range than deeper in. One way of treating this analytically is to idealize a bombarded target as consisting of the sequence surface/damage/no-damage. It is shown that the interface damage/no-damage then acts as a nearly impermeable barrier and thus tends to prevent inward motion. Alternatively, one can approximate the detrapping energy as varying continuously with depth, ΔH = ΔH 0(1-gx), the problem then becoming one of solving the equation ∂C/∂t = D (∂2 C/∂s 2 -∂C/s∂s), where s=exp (-ΔH 0 gx/2RT). The interesting resul...