Fundamental parameters

The mean attachment energies are [BUR 51]:

Hence, the activation energy for diffusion:

From this, we can deduce the diffusivity on the surface: a: molecule dimension (part of a multilayer) (m)

v: vibration frequency of an atom or a molecule in position (s^-1) Frequency v increases with molecule complexity:

The characteristic length for surface diffusion is:

Hence:

The activation energy AGmche is equal to 1/4 of the energy 2ф required for moving a molecule from a position on this step towards a cavity on the same step.

NOTE.-

Surface energy.

Through the following, the superficial energy of a crystal is:

The energy use per unit of step length (edge unit) is:

Indeed, ji = ya, where a is the dimension of one molecule. We can refer to the publication of Nielsen et al. [NIE 71] for the various values of y.

Growth of a K face

[MUT 01, p. 294].

Example 2.3.-

This is an absurd result. Consequently, we will involve the diffusion layer in the following example:

Example II-

As the kinetics are particularly fast, we can accept that: