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Table 4.1.: Parameters for stoichiometric EuO on cubic substrates by Oxide MBE. UHV conditions are
required and gas nozzles are employed. YSZ provides oxygen to the initial EuO layers.
EuO growth partial EuO growth
substrate initiation T S flux density of Eu pressure O 2 termination
YSZ (9%) 30–60 s Eu 350–450 ◦ C 2.77 × 10 13 Eu/cm 2 s 1.3–1.7 × 10 −9 Torr 10–60 s Eu
cYSZ, LAO, MgO 0–30 s Eu 350–450 ◦ C 2.77 × 10 13 Eu/cm 2 s 1.3–1.7 × 10 −9 Torr 10–60 s Eu
Substrates of cubic oxides (YSZ, LAO, or MgO) are cleaned in iso-propanol, followed by an
in situ annealing step at elevated temperature (T S = 600 ◦ C) under O 2 supply. In this way,
we obtain atomically smooth surfaces, for which RHEED pattern confirm the expected cubic
(100) surface structure. A consistent application of the Eu distillation condition, 32,45 in
which at elevated temperature any excess Eu metal is evaporated, ensures a stoichiometric
composition of the EuO thin film during MBE synthesis. For this approach, Eu metal (purity
99.99%) is e-beam evaporated with a constant flux density (Φ Eu = 2.77 × 10 13 Eu/cm 2 s) under
ultra-high vacuum (p base 1 × 10 −10 mbar) onto the surface of the heated oxide substrate
(T S = 350–450 ◦ C).
A limited supply of molecular oxygen (purity 99.999%), which is leaked into the main deposition
chamber via specialized oxygen distribution nozzles (described in Sec. 3.3 on p. 42), initiates
the reaction to EuO, this approach is referred to as “adsorption-controlled deposition”. 25
Stoichiometric EuO is obtained by the supply of O 2 in the range 1.3–1.7 × 10 −9 Torr. In order
to obtain chemically well-defined interfaces, before and after the adsorption-controlled
deposition of EuO, we supply excess Eu in the monolayer regime as a seed for epitaxial EuO
and as an oxidation protection after O 2 supply has been terminated.
Finally, we apply an air-protective metallic cap, prefereably Al or Si.