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

dE/dx (ev/Ang)
10
1
Inelastic Energy loss for H and He in Si
He
H
Lindhard and Scharff
V TF (H + )
0.1 1 10 100 1000 10000 100000
Energy (keV)
Electronic stopping depends on the electronic states in the target so that in
principle gas, liquid, and solid of the same element must have different stopping cross
sections. The nature of the chemical binding also affects the electronic states. Both of
these effects however are weak.
2.3.3 Experimentally obtained stopping powers
As well the large amount of theoretical information available on the magnitude
of the stopping powers available, experimental measurements can be carried out to
determine stopping powers. Averages of the best experimental and theoretical stopping
power values have been produced and can be tabulated using the SRIM programs (3, 8).
The MEIS analysis in this thesis has used the SRIM values for the inelastic stopping
powers.
2.3.4 Difference in stopping powers in open channels
Along the open crystal channels the electron densities are reduced. This has the
effect of reducing the rate of inelastic energy loss compared to a random direction (25).
R is defined as the ratio of the energy loss in an open channel to the energy loss in a
24
V TF (He + )
Bethe - Bloch
Figure 2.3 Electronic stopping powers for H and He ions in Si. The positions
corresponding to the Thomas Fermi velocity are indicated, along with the energy
regimes where different models for the stopping powers are applicable.