3.2 Characterization techniques 51
Figure 3.5: Schematic of the Glancing Angle XRD setup. This technique is also
called Grazing Incidence XRD. A low incoming angle is kept constant throughout
the measurement, minimizing the signal contribution from the substrate.
constraints in the choice of sample and substrate. In general, when the lms are
below 100 nm setting an of around 0.5 degrees results in high signal to noise
ratios but the surface must have a low roughness. This is due to diculties in
alignment, where it must be ensured that an optimum amount of the incoming
X-rays are hitting the surface of the sample instead of just below or above. An
important part of this alignment procedure is therefore to adjust the height of
the sample holder.
3.2.2.2 Crystalline manganese oxides
The majority of results in this project have been obtained with a highly disordered
manganese oxide denoted MnOx. This is due to the ease of preparation
and less interaction with the substrate when deposition temperature is kept below
200 oC during deposition. For carbon based substrates the Mn lm catalyses
the formation of CO2 in oxygen containing atmospheres, which leads to significant
roughness and Mn being covered with carbon. The substrates used for
EQCM measurements on the other hand could sustain a maximum temperature
of 400 oC due to surface segregation of Ti forming TiO2 at the surface. Despite
these issues some time was spent on trying to identify conditions for crystalline
Mn oxide deposition. The results are summarized in table 3.2.
3.2.3 X-ray Absorption Spectroscopy
The technique X-ray Absorption Spectroscopy, XAS, can be used to probe electronic
structure and local geometry of matter 196. It relies on high resolution
X-rays in the range of 0.1 to 500 keV. The requirements for the radiation are:
a) high X-ray ux so that good signal to noise ratio is obtained in a reasonable
time, b) broad spectral range with uniform ux so a suitable spectrum can be