[LIYAFEI]

Hallow everyone

Recently, I want to simulate the CVD process with reacting. There are 2 steps of the reaction.
For example
1st, A(gas) +B(gas) = C (gas)
2nd, C(gas) +D(gas) =E (solid) (only on the substrate)

I put a small (10*10mm) substrate in the tube (I.D.20mm * Length 400mm).

So how should I make the code to limit the 2nd step on the surface of substrate?

Is there a simple example?

Thank you very much.
Yours
Li