Analysis of the extended defects in 3C-SiC.pdf - Nelson Mandela ...

3.1. Introduction
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CHAPTER THREE
ION IMPLANTATION AND RADIATION DAMAGE
In this chapter a model of the implantation of ions into matter and the subsequent
radiation damage is presented. Theories for the calculation of ion ranges are discussed
and reference is made to the most popular approach, that of the LSS theory, to
illustrate the procedure taken in doing such a calculation. The result shown in Chapter
6 was however obtained using software developed by Ziegler et al. (1985) using
Monte Carlo methods. Following this theory of displacement damage and annealing
of defects are presented.
3.2. Ion ranges
3.2.1 Introduction
During ion implantation, the implanted species can lose energy to the target atoms in
two ways, namely electronic excitations (inelastic) and nuclear collisions (elastic). At
higher energies the ion is stripped of some or all of its electrons and multiply ionized
at which stage the energy loss is mainly due to inelastic processes, i.e. electronic
excitation. Occasionally the moving atom will interact directly with lattice atoms and
collisions of the Rutherford type results. As the kinetic energy of the moving atom
decreases its degree of ionization does as well until the atom essentially becomes
neutral at which stage collisions of the hard-sphere type will dominate. The rate at
which energy is lost is given in the following form,
dE
N[
S n ( E)
Se
( E)]
(3.1)
dx
where N is the number of target atoms per unit volume, Sn(E) and Se(E) defined as the
nuclear and electronic stopping powers respectively. The nuclear stopping power
Sn(E) is given by,