Oxidation von Eisenschichten auf MgO(001)-Substraten - Universität ...

8. Summary
ratio of Fe 2+ / Fe 3+ is almost the same regardless of the substrate temperature. It was also
discovered that there are Mg 2+ -ions on the surface of these samples at a high temperature(573
K). The LEED diffraction patterns of the reactively deposited films showed that crystalline
iron oxide layers were formed independently of the temperature. It could also be observed
that the crystallinity of the deposited iron oxide films increased with increasing temperature.
The LEED diffraction pattern of the iron oxide film deposited at RT showed a (2 × 1)
structure with two domains. At 373 K, the prepared sample had a (2 × 1) structure with
two domains but with smaller reflexes. These structures can not be assigned to an iron oxide
phase. The surface of the iron oxide film deposited at 473 K showed a (2 × 2) structure
with a ( √ 2 × √ 2)R45 ◦ superstructure. This is the structure of magnetite described in the
literature [31]. However, the composition of this film did not match the one for magnetite.
An explanation for this contradicting results may be that during film deposition wustite is
formed initially followed by a magnetite film on top. The iron oxide film reactively prepared
at 573 K showed a (2 × 2) structure. This structure is required for maghemite [31]. However,
the particular ion ratio of Fe 3+ / Fe 2+ did not correspond to maghemite. In this case, a layer
system of wustite and maghemite can be assumed to establish a link between XPS and LEED
results.
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