Surface Species
For each of the k Surface Species the following equations are solved:
where Zk is the site fraction (dimensionless), Rsurf,k is the surface rate expression (SI unit: mol/m2) and Γtot is the total surface site concentration, as specified in the Surface Chemistry section of the physics interface settings. In the Plasma, Time-Periodic interface surface sites are assumed to be constant along the period and Rsurf,k is replaced by its period averaged
The quantity Zk is the surface equivalent of the mole fraction on the volumetric level. That is, the sum of the site fractions must always equal one:
.
Empty sites are not accounted for in reaction rate coefficients, so all species which can occupy a surface must be included in the model. The surface site concentration is given by
.
where σk is the site occupancy number. For each of the bulk surface species, the following equation is solved for the deposition height:
where hk is the total growth height (SI unit: m), Mk is the molecular weight (SI unit: kg/mol), and ρ is the density of the bulk species (SI unit: kg/m3).