Ion implantation is a forced process by which ions are violently inserted into the structure of material. The driving force is acceleration of these ions and impact on the surface, forcing their way towards the subsurface. Diffusion is a natural process by which ions move in the porosity of a material. The driving force here is a concentration gradient, and diffusion tends to make the concentration homogeneous at each point. Diffusion is possible only if the material presents a non-zero permeability, whereas implantation corresponds to an insertion of ions in the structure, pushing the atoms apart, even if no porosity is present.

Alain

Ion implantation is a forced process by which ions are violently inserted into the structure of material. The driving force is acceleration of these ions and impact on the surface, forcing their way towards the subsurface. Diffusion is a natural process by which ions move in the porosity of a material. The driving force here is a concentration gradient, and diffusion tends to make the concentration homogeneous at each point. Diffusion is possible only if the material presents a non-zero permeability, whereas implantation corresponds to an insertion of ions in the structure, pushing the atoms apart, even if no porosity is present.

Alain

Dear Alain, I am completely surprised when you talk about the porosity as  the potential sites  for the diffusing  of atomic  species in  the  solids, which have  well define lattice structures!!!  In Physical Metallurgy and Materials science,  the porosity is macroscopic bulk defect, which has well defined volume and surface.  Foreign species like impinging ions after they become thermalized  they occupy either the substitution  or  interstitial sites in the lattice structure according to their  atomic sizes with respect to available sites in the Xtal  or else they may form clusters, and sometimes they may create extrinsic stacking faults.

The permeability is a process, which is controlled by diffusion of  the chemical species  through  the bulk  solid  as well as the dissociative  reaction taking place at the interface between solid and gas phases etc.  Mostly surface reactions are fast compared to the diffusion, and overall process becomes diffusion controlled. Such as diffusion of Hydrogen dissociation,   H2  = 2 H+  + 2  e-  at the surface, and diffusion of proton by the hopping motion  from one tetrahedral site to another tetrahedral site passing through the activation energy barrier with the help of the localized  thermal fluctuation.

Best Regards

Tarık

Note: In the case of amorphous solids still we talk about  the atomic defects such as the vacancy clusters  ( relaxators)  as the potential sites for the diffusion species in the bulk system driven by not only concentration gradient but also by the external driving forces such as the stress gradient etc.

One should not forget the real  driving force is the gradient of the chemical potential and not the concentration gradient always. There are case where diffusion takes place against the gradient of concentration gradient (Up Hill diffusion of carbon in FeSiC alloy)!!!

Porosity can be understood as true porosity, but also as vacancies. Interstitial movement requires much smaller species, e.h. H+ indeed.

Alain

 Dear Professor Celzard; You are French speaking person, and your scientific interests deal with disordered, porous and related materials etc.  I wouldn’t not surprise that you wish to call vacancies as atomic size porosities.  These two words they have nothing in common in modern English language but it may in French: VACANT   ROOM doesn't'   imply Porous ROOM? In English.  If you use that by mistake in TX they will knock you out!!, which happened to me in early  sixties.

Note: porous which was taken from French to Middle English similar to Vacant, it   has  an origin in Latin: porus and in Greek: poros. İt means small opening through which matter and animal can go, etc.  Vacancy:=  empty or free space, idleness  etc.  

Dear Dr. Kudriavtsev,  I am sorry to say that the diffusion is a typical nonequilibrium process, which  takes place under the non-vanishing  chemical potential gradients (as well as in the stress, temperature and electrostatic  field gradients)  .[1]  And  the implantation is a dynamical process far from the equilibrium up to the point of where we can talk about the thermalization, then it  can  be treated as an irreversible process!  Best regards

[1] S.R. de Groot, Thermodynamics of Irreversible Processes, Chapter VII, pp. 94-136

Dr. Omer Ogurtani. You are right, diffusion is no-equilibrium process.

Dear Dr. Kudriavtsev, I  thank you since you haven't overlooked  some thing was false to be published at this platform!  Also,  I am  amazed   that Dr. Celzard didn't show any attempt to correct his false statement to stay at this platform even after my reference to the Professor de Groot'  highly respected  book!