:: IPCI ::

Surface reactions (heterogeneous) :

Surface adsorption SiH_2(g)↔ SiH_2(a)
- Physical adsorbtion (weak forces beatween molecules)
- Chemisorption (chemical bonds between atoms)
- The sticking coefficient (0 < γ < 1) defines the capacity of molecules to adhere to the surface
  - it has an Arrhenius dependence on temperature
Diffusion on the surface - diffusion coefficient has also an Arrhenius dependence on temperature, increasing with temperature
Surface reaction - reaction rate has also an Arrhenius dependence on temperature (therefore temperature is neede for diffusion of atoms on the surface and for chemical reactions)
- SiH_2(a)→ Si_(s) + H_2(a)

Desorption - hydrogen in the case of Si deposition is desorbed from the surface - temperature is also needed for this reaction
- H_2(a) → H_2(g)
- H + H → H_2(g)

In the picture is shwon how the SiH₂ molecules arrive at the Si surface which is saturated with hydrogen. The hydrogen is desorbed and Si takes its place.