ASYMPTOTIC ANALYSIS OF SOME 2-DIMENSIONAL DIFFUSION-PROBLEMS

In this paper we discuss two-dimensional surface source and implant pr oblems for a substitutional-interstitial diffusion model. We present a symptotic solutions in the limit of the surface concentration of impur ity (or peak concentration of the implant) being far greater than the equilibrium vacancy concentration. Using leading order composite solut ions we plot contours of constant impurity concentration. Some of thes e contours differ markedly from those of the corresponding linear prob lem, having the 'bird's beak' shape which is frequently observed in ex periments. We also discuss a two-dimensional surface source problem fo r a vacancy model.