Growth and Characterisation Studies of Eu$_3$O$_4$ Thin Films Grown on Si/SiO$_2$ and Graphene

TL;DR

This study explores the growth, structure, and magnetic properties of Eu$_3$O$_4$ thin films on Si/SiO$_2$ and graphene, revealing their crystallinity, magnetic behavior, and compatibility with graphene without damaging it.

Contribution

First demonstration of Eu$_3$O$_4$ thin films grown on graphene with preserved properties and detailed analysis of their structural and magnetic characteristics.

Findings

Eu$_3$O$_4$ films are highly textured and crystalline on both substrates.

Both films exhibit a Curie temperature of about 5.5 K.

No metamagnetic behavior observed in films, unlike bulk Eu$_3$O$_4$.

Abstract

We report the growth, structural and magnetic properties of the less studied Eu-oxide phase, Eu$_3$O$_4$, thin films grown on a Si/SiO$_2$ substrate and Si/SiO$_2$/graphene using molecular beam epitaxy. The X-ray diffraction scans show that highly-textured crystalline Eu$_3$O$_4$(001) films are grown on both substrates, whereas the film deposited on graphene has a better crystallinity than that grown on the Si/SiO$_2$ substrate. The SQUID measurements show that both films have a Curie temperature of about 5.5 K, with a magnetic moment of 0.0032 emu/g at 2 K. The mixed-valency of the Eu cations has been confirmed by the qualitative analysis of the depth-profile X-ray photoelectron spectroscopy measurements with the Eu$^{2+}$ : Eu$^{3+}$ ratio of 28 : 72. However, surprisingly, our films show no metamagnetic behaviour as reported for the bulk and powder form. Furthermore, the Raman spectroscopy scans show that the growth of the Eu$_3$O$_4$ thin films has no damaging effect on the underlayer graphene sheet. Therefore, the graphene layer is expected to retain its properties.