Fabrication of the next generation silicon devices requires fundamental understanding of defect interactions that are characteristic of nano-scale device processing. Because a variety of intrinsic and extrinsic defects generated at surfaces and interfaces can easily diffuse and reach the active regions in the nano-scale devices, it becomes crucial to understand the transient and non-equilibrium behaviors of defect interactions related to nano-scale fabrications. In order to identify what types of kinetics and reactions are relevant to nano-processing, diffusion in silicon and silicon oxide is studied using isotopically controlled silicon heterostructures. Our experiments probing the effect of interfaces on impurity and silicon self-diffusion in silicon dioxide, silicon self-diffusion in silicon, and implanted-impurity and silicon interactions are reviewed. Then quantitative models based on such experimental studies are presented and how they will be utilized in the construction of diffusion simulators is discussed.