Chemistry Reference
In-Depth Information
technique became popular, it soon became clear that the atomic configuration of
the implanted atom cannot easily be predicted and that the implantation process
can lead to extensive damage. Hence room for scientific research on the ion
implantation process itself and on the fate of the implanted ion.
Although ion implantation received its main impetus as a technique to dope
semiconductors, its use was not limited to this field. When implanting high enough
fluencies in semiconductors, it was found that the technique could be used to
synthesise conductive layers at well-defined depth inside the semiconductor host,
opening a semiconductor technology field of study of its own.
Also ion implantation into metals and insulators was studied. Just as in the case
of semiconductors, at low fluencies this allowed to study the atomic configuration
around the implanted ion and its defect association. A special field of study was the
investigation of the huge internal magnetic fields that implanted atoms were found
to experience in magnetic hosts like Fe, Ni and Co. At high fluencies intermetallic
surface layers could be formed, and also phenomena like surface hardening and
corrosion resistance upon implantation e.g. steel with nitrogen were intensively
studied.
This tutorial will not attempt to deal with all these ion implantation phenomena,
although Mössbauer spectroscopy has been used in all these fields. We will give
several illustrative examples but we will mainly focus on semiconductors and to
rather low implantation fluences where the implanted atoms are still isolated from
each other or just start to coalesce and to form precipitates. The phenomena at high
fluences and the dynamics of compound layer formation are beyond the scope of
this tutorial. The reason for this limitation is that emission Mössbauer spectros-
copy on radioactive probe atoms is particularly powerful in this low concentration
range and allows to study the more fundamental phenomena of lattice location and
defect association at the individual probe level, which is hard to study with other
techniques. On the other hand, experience has shown that one has to be extremely
careful in drawing conclusions from Mössbauer spectroscopy results only, as the
possible interpretation of a particular Mössbauer spectrum is often not unique.
Complementary data, e.g. from electron microscopy, X-ray diffraction, transport
measurements, channelling experiments, are often more than welcome or even
crucial for the interpretation of the hyperfine interaction data.
6.1.1 Probing Local Structures and Their Dynamics
Natural science begins with ''seeing''. Eyes provide you a first tool to discover
wonders of nature. Everyone should have experienced to magnify dragonfly's eyes
and crystals in rocks by loupes, or to watch the surface of the moon and the circle
of Saturn by telescope. Nowadays, ''electron microscope'' and ''scanning probe
microscope'' enable us not only to ''see'' atoms and their arrangements in mate-
rials, but also to manipulate them, in order to create new functional materials and
biomaterials.
Modern
''nanoscience''
and
''nanotechnology''
began
with
the
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