Ion implantation and diffusion which occur during irradiation are investigated through out series of related processes. In our study, the whole process will be viewed as a two-step process. The first includes the implantation process. The equation of motion for ion implantation is considered as a modified form of Fick's law, which solved analytically taking the sputtering process into account. The second step i.e. the step of ion-redistribution through out diffusion is studied keeping in mind that the total number of impurities is conserved in the step of injection and diffusion. The case of diffusion-concentration dependence and the suitable equation for thermal diffusion is studied too. The steady state situation is studied extendedly. The diffusion in multilayer structure and a useful introduction about hererostructures is given with important related effects are presented. Extended theoretical treatment concerned with the extension to multilayer structures is presented. The case of "constant-surface-concentration-diffusion" is treated by considering the surface to be covered with certain type of adatoms. The coverage-dependent diffusion is modeled by assuming certain form