Damage formation and annealing studies of low energy ion implants ...

energy than one scattered from an atom of the same element at the surface, for the same
scattering angle. Comparison of the additional energy lost and knowledge of the rate of
inelastic energy loss allows the depth at which scattering occurred to be determined.
The rate of inelastic energy loss (dE/dx), is most conveniently expressed in units
of eV/Å, and is dependent on the ion, the target material and the ion energy. The
accuracy of the depth scale calibration is obviously limited by the accuracy of the
stopping powers used. Work has been done by Andersen and Ziegler to average the best
available experimental and theoretical stopping power values and these stopping power
values can be obtained from the SRIM 2003 program (20). The appropriateness of the
values used is discussed in section 4.2.3.1 later. Values of the inelastic energy loss for H
and He ions in Si are shown in Figure 4.1 for the energy range 0 to 400 keV.
Inelastic energy loss (eV/Ang)
35
30
25
20
15
10
5
He in Si
He in SiO 2
H in Si
0
0 50 100 150 200 250 300 350 400
Energy (keV)
Figure 4.1 Inelastic energy loss rates as a function of energy for H in Si and He in Si
and SiO2.
Deviations in the stopping powers from pure Si targets may arise when a
sufficient amount of another element is present. In these studies however, the samples
do not have a high enough concentration of any element other than Si to significantly
alter the energy loss rates and hence the depth scales. For the case of an extremely high
concentration of another element present the stopping of a compound may be estimated
by the linear combination of the stopping powers of individual elements, known as
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