Association

4.2. Lateral tensile strain: EuO on LaAl 3 (100) 75
Figure 4.15.: EuO/LAO (100): process of strained EuO deposition. On oxygen-annealed LAO (100),
EuO is grown via the Eu distillation condition. Beginning from one monolayer, EuO adapts
the in-plane lattice parameter of LAO. LEED and RHEED pattern confirm the EuO/LAO (100)
heteroepitaxy and display an fcc lattice for every stage of a sustained EuO growth.
LEED and RHEED pattern. Applying the Eu-distillation condition with limited oxygen supply
(adsorption-controlled growth), a 16 nm-thick EuO film is grown onto annealed LAO
(100). Beginning from the very first monolayer of EuO – thus showing no interstitial stages -
– the RHEED streaks indicate a smooth and crystalline surface at every stage of EuO growth,
and the RHEED patterns show the same reciprocal space distance as for the LAO (100) surface.
This is an evidence for the adaption of the LAO lateral lattice parameter by the EuO
layer. LEED patterns were recorded after growth of a 4 nm and of a 16 nm EuO thick film.
Both indicate a good crystallinity of the EuO fcc lattice without any other phases. These electron
diffraction results prove that it is possible to grow epitaxial and single-crystalline EuO
on LAO (100).
X-ray diffraction of the 16 nm epitaxial EuO layer (Fig. 4.16a) shows exclusively the cubic
(a)
10 5
(b)
10 7
intensity (counts)
10 4
10 3
10 2
10 1
10 0
30
EuO (200)
40
10 6 90
LAO (200) EuO (400) LAO (300)
50 60 70 80
10 6
10 5
10 4
10 3
10 2
10 8 2.5
critical angle
XRR
simulation
0.5 1.0 1.5
EuO
Kiessig fringes
2.0
2 theta (°)
2 theta (°)
Figure 4.16.: EuO/LAO (100) investigation of the perpendicular lattice parameter, and layer thickness
and roughness. In (a), a 2θ wide scan reveals the perpendicular lattice parameter of the LAO
(100) substrate and single-crystalline EuO (100). This multilayer structure is characterized by
X-ray reflectivity (b) which reveals density ρ, thickness d, and roughness σ of each slab.