Surface scattering is modeled by the following empirical
The function depending on the surface distance describes a smooth
transition between the surface and bulk mobility [174,175].
describes a critical length.
The pressing forces and in (3.118) are equal to
the magnitude of the normal field strength at the interface if the carriers are
attracted by the interface, otherwise zero.
Parameter values for surface mobility reduction in Si - MINIMOS 6 model
220.127.116.11 Lombardi Mobility Model
Lombardiet al.  suggested
another surface mobility degradation model. There are two surface scattering
contributions due to acoustic phonons, , and surface roughness,
. They are functions of total doping concentration and
the pressing forces and .
The total mobility is expressed by a Mathiessen rule:
Parameter values for surface mobility reduction in Si - Lombardi model