Dear Prateek Kothari

Many thanks for the reply but I think, I should explain a little. My question is about Interstitial and substitutional diffusion mechanism. If a dopant comes in contact with Silicon then what is the preference diffusion mechanism ? Interstitial or substitutional? What are the rules, a dopant has to follow to move into the crystal lattice of the silicon ? If you think of Hume-Rothery Rules for substitutional diffusion then the dopant do not fit into this criteria (fitting parameters of dopant element into this rule are attached already)

Please explain in this context, if possible.