Chemistry Reference
In-Depth Information
Fig. 6.26 Mössbauer set-up
scheme at RIKEN
period of the landing processes, the nuclear probe will find different lattice sites
close to this damage region either by landing directly on interstitial sites, or by
substituting host atoms. In the case of
57
Mn implantation, the b-decay from
57
Mn
to
57
Fe causes an additional small turbulence on the lattice sites of the probe, i.e., a
recoil process of
57
Mn probe when emitting a highly energetic electron. The
experimental results will tell us about the lattice sites as well as the charge states,
as will be given in the followings.
Starting with a primary beam of
58
Fe,
57
Mn beam will be produced through the
projectile fragmentation following a reaction with a Be target. Subsequently, the
fragment of
57
Mn nuclei will be implanted into a sample, and will be stopped
deeply in the matrix with an order of hundreds lm from the surface. The stopping
range and their struggling, which are evaluated by TRIM code [
9
], are shown in
Fig.
6.27
for the case of a Si crystal, and the result is compared with that of
100 keV-
57
Fe implantation. Since the ion range of
57
Mn is 4 orders of magnitude
higher than that of conventional low energy implantation, as described in the
sections before, yielding us unique experimental conditions such as the low con-
centrations of
57
Mn as well as defects. One would speculate that GeV-implantation
would produce only ''amorphous'', and therefore, no atomistic information could
be studied through Mössbauer spectroscopy. The experimental results have,
however, showed that we can send our ''spy'', i.e.,
57
Mn/
57
Fe deeply into the
sample, and the spy send us, indeed, unique atomistic information on the nuclear
probes and their surrounding lattice in Si materials.
57
Mn/
57
Fe Experiments on Si
6.5.2
As stated before, iron impurities in Si have been intensively investigated for more
than 50 years by different experimental techniques [
44
] including
57
Fe Mössbauer
spectroscopy. This is because Fe impurities can be easily incorporated into Si
