As and Epitaxial-Growth MnSi Thin Films - OPUS Würzburg

6.2. Material Characterization 71
Fig. 6.3: XRR measurement of the 20-nm layer with superimposed two-layer simulated curve.
The extracted layer thickness agrees with the XRD measurements of the same film. Other
parameters such as cap thickness and interface and surface roughness were extracted for a fuller
description of the physical characteristics of the layer. Measurements and figures reprinted with
permission from C.Pohl of EPIII.
characteristics of the grown films to literature values for both bulk and thin film MnSi.
Shown in Figure 6.2 are the results of the XRD and XRR measurements performed by C.
Pohl of EPIII. Here we discuss key results which would strongly suggest the grown films
as epitaxially-grown thin layers of MnSi. In Figure 6.2, the ω−2Θ XRD data on the left
shows the MnSi peak in the ω scan with the peaks (in red) for Mn 3 Si 5 for comparison.
On the right is an ω − 2Θ scan on the 20-nm layer showing pseudo-Voigt fit showing
good fit. The scan shows fringes on both sides and the fringe period calculated from
the fitting corresponds to a thickness of 20.6 nm. From the XRD measurements, several
other characteristics of the film can also be extracted such as the average lattice constant
and crystallographic relation of the grown film in relation to the Si[111] substrate. The
measured crystallographic orientation of the grown films follow MnSi[111]‖Si[111] and
MnSi[2¯1¯1]‖Si[10¯1], consistent with [Zhan 02] and [Suto 09]. The average measured lattice
constant is 4.545Å, -0.34% off from the literature value. Of course, the presence of other
(non-magnetic) Mn:Si stoichiometries arestill possible andcanonly beresolved by further
testing, especially high resolution TEM imaging for checking crystallinity, etc.
The XRR measurement on the 20-nm layer is shown Figure 6.3 with fitting to extract
physical parameters of the film. Using a two layer model to simulate the layers, good fit
with the experimental data is achieved. The oscillations of the cap layer is superimposed
with those of the MnSi layer. Fromthe XRR measurement, the following parameters were
extracted: thickness d MnSi = 20 nm (nominal: 20.6 nm), (amorphous) Si cap thickness
d Sicap = 7.9 nm (nominal: 7 nm), interface roughness MnSi/Si cap = 0.1 nm and surface
roughness ∆ MnSi = 0.1 nm.
The XRD and XRR measurements show strong indication of MnSi presence within the
grown layers, consistent with literature values which bodes well with the establishment
of growth parameters of the material. Both measurements show a relatively homoge-