2 Illustration of the Physical Process
An illustration of the
effects of energy and material deposition on the mixing on a simple
target material is shown in figure 2.
The original material structure
consists of a material M3 with a single layer of a mixture of
a material M2 with M3 (in ratio 40:60) and it is
bombarded with species of material M1, the primary particles.
Sharp interfaces that define the layer.
In figure 2(a) the original material
structure is shown.
At dose f = 0 the particle yield will
only consist of species M3, since all the particles in the near-surface
region are of material M3.
The effect of the incident
particles on the layer of material M2/M3 is negligible as the
energy and range functions of the bombarding particles
are not significant there.
A typical situation at dose f1 is shown in figure 2(b).
The physical process causes the surface to recede. The bombarding
or primary species accumulates in the surface region to give the
concentration curve q1(X).
In order to accommodate the primary material,
the concentration of the material q3(X) has been reduced
from unity. In turn, the yield
concentration of species M3 is reduced from the initial dose level and
the yield of the primary species is increased.
In figure 2(c) a small concentration of material M2 has reached the surface
layer and the yield now consists of particles of all three species.
The energy deposition is now also affecting the second interface,
which has become slightly smoothed.
Figure 2. (a) Original material structure; (b) material distribution and particle emision at dose phi_1; (c) material distribution and particle emision at dose phi_2.