Since many years, the importance of thin layers increases for lots of
technical uses. Beginning in the field of microelectronics, the use of thin
layers spread increasingly to other areas. Coatings for surface refining and
optimisation of the mechanical properties for material engineering,
customisation of the surface chemistry in catalysts, as well influencing of
the transmission and reflection characteristics of surfaces in optics are
only some examples of the high scientific and economic weight of the thin
layer technology. Thin magnetic layers are the basis of many known
storage media ranging from the tape recorder to the hard disk up to the
credit card. Nowadays, these thin layers again gain interest in the research
field of nanoelectronics as ultrathin layers. So-called spinvalve-read/write
heads being already installed in actual hard disks use the Tunnel Magneto
Resistance effect for a significant rise in memory density synonymous
capacity. Such read/writeheads consist of a magnetic layersystem. This
use of the magnetic as well as the electric characteristics of the electrons
is called spintronics. The iron oxide magnetite exhibits a high iron portion,
is strong antiferrimagnetic and has a high Curie-temperature. Since many
years, it is used as a magnetic pigment on already mentioned magnetic
tapes. Literature [1, 2, 3, 4] considers ultrathin epitaxial layers of magnetite
on magnesium oxide for uses in the spintronics as a most promising
candidate, because it inheres a complete spin polarisation at Fermi-level.
Moreover, thin magnetite layers serve in the chemical industry as a catalyst
in the Haber- Bosch-procedure and to the dehydration of ethylbenzene to
styrene. Being already used and considered to be of ongoing interest,
ultrathin magnetite layers offer a wide range of technological applications in
many modern industrial and scientific fields. Because there is,
nevertheless, a variety of other iron oxide (cf. chapter 4), it is a matter to
determine the special growth conditions of magnetite. These ultrathin iron
oxide layers were grown reactively on the (001)-surfaces of the magnesium
oxide substrate by molecular beam epitaxy. Besides, the surface is
examined by the diffraction of low-energy electrons concerning its
crystalline structure. X-ray photo electron spectroscopy approaching the
stochiometry completes these first characterisations. Other investigations
are carried out at HASYLAB / DESY in Hamburg by X-ray reflectivity and X-ray
diffraction. The exact thickness of the layers, its crystal properties in bulk, as
well as the thickness of the crystalline portion of the layers can be
determined among other features of the system. The evaluation of XRR-and XRD-investigations is done via simulations with in chapter 5
introduced software packages. The reader finds the theoretical
backgrounds to the used techniques in chapter 3. The experimental setups
in Osnabr¨uck and Hamburg as well as the backgrounds to the
preparation are presented in chapter 5. Because the formation of the
different iron oxides is described in literature [5, 6, 7, 8] as mostly
depending on annealing temperatures, the experimental results in chapter
6 are graded accordingly. The dependence on temperature, layer thickness
and annealing time should be examined for the iron oxides possible on
this substrate. The aim of this work is the preparation of ultrathin epitaxial
iron oxide layers with thicknesses up to few nanometers. The main goal is
to find the growth parameters for ultrathin crystalline magnetite
layers.
| Identifer | oai:union.ndltd.org:uni-osnabrueck.de/oai:repositorium.ub.uni-osnabrueck.de:urn:nbn:de:gbv:700-201009176491 |
| Date | 17 September 2010 |
| Creators | Zimmermann, Bernd Josef |
| Contributors | Prof. Dr. rer. nat. Joachim Wollschläger, Prof. Prof. h.c. Dr. Dr. h.c. Manfred Neumann |
| Source Sets | Universität Osnabrück |
| Language | German |
| Detected Language | English |
| Type | doc-type:doctoralThesis |
| Format | application/pdf, application/zip |
| Rights | http://rightsstatements.org/vocab/InC/1.0/ |
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