Temperature dependent epitaxial growth regimes of europium on the oxygen-induced c(6×2) reconstructed (110)Nb surface

• Fcc Eu islands are epitaxially grown on the c(6×2) reconstructed (110)Nb surface at 260 °C.
• The intermediate phase formed at 150 °C on the c(6×2) reconstructed (110)Nb surface is identified.
• The formation of EuO interface at 260 °C is unambiguously evidenced.

We present epitaxial growth of europium (Eu) on the oxygen-induced c(6×2) reconstructed (110)Nb (niobium) surface at 150 °C and at 260 °C for various Eu coverages. The samples are characterized by reflection high-energy electron diffraction, atomic force microscopy and low-temperature in-situ nuclear resonance scattering. At a substrate temperature of 260 °C Eu forms islands with the face-centered cubic (fcc) crystal structure that is an exotic crystallographic phase for metallic europium. The deposition at 150 °C results to the already reported formation of a smooth film with hexagonal symmetry. The up to now unknown initially formed intermediate phase in this growth mode is identified as EuO-type stacking of [111]Eu layers that quickly relaxes towards that of an [0001]Eu film. The analysis of the nuclear resonance scattering data unambiguously demonstrates the formation of EuO interface at 260 °C that facilitates the stabilization of the strained fcc Eu lattice. No traces of EuO are found in the sample grown at 150 °C.