High-quality EuO thin films the easy way via topotactic transformation

Abstract

Epitaxy is widely employed to create highly oriented crystalline films. A less appreciated, but nonetheless powerful means of creating such films is via topotactic transformation, in which a chemical reaction transforms a single crystal of one phase into a single crystal of a different phase, which inherits its orientation from the original crystal. Topotactic reactions may be applied to epitactic films to substitute, add or remove ions to yield epitactic films of different phases. Here we exploit a topotactic reduction reaction to provide a non-ultra-high vacuum (UHV) means of growing highly oriented single crystalline thin films of the easily over-oxidized half-metallic semiconductor europium monoxide (EuO) with a perfection rivalling that of the best films of the same material grown by molecular-beam epitaxy or UHV pulsed-laser deposition. As the technique only requires high-vacuum deposition equipment, it has the potential to drastically improve the accessibility of high-quality single crystalline films of EuO as well as other difficult-to-synthesize compounds.

Oxide Materials at the Two-Dimensional Limit

“…In general, EuO epitaxy must be carefully controlled with regards to temperature, deposition rate, and oxygen pressure to preserve the Eu 2+ oxidation state; metallic Eu 0 has a low sticking coefficient [194], while over-oxidized Eu 3+ is paramagnetic [195]. Here, we build upon the previous multi-metal study [184] The EuO films crystallize in the rock salt structure (Space group Fm3m [196]) and the primary unit cell axis is rotated by 45° with respect to the unit cell axis of substrate surface to minimize lattice mismatch (22% down to ~7%).…”

Nanomorphology Effects in Semiconductors with Native Ferromagnetism: Hierarchical Europium (II) Oxide Tubes Prepared via a Topotactic Nanostructure Transition

“…Despite the exceptional properties of EuO almost nothing is known when it comes to nanomaterials, except for thin films prepared by ultrahigh vacuum deposition methods . The difficulties in preparing nanostructured EuO are caused by the required high temperatures (1200 K) and the need for a very precise control of stoichiometry .…”

Reversible control of magnetism in La0.67Sr0.33MnO3 through chemically-induced oxygen migration

“…[17][18][19][20][21][22] It is likely, therefore, that the deposition of a strongly reducing Gd film on an oxide with high oxygen mobility will induce significant oxygen migration and alter the magnetic properties. [23][24][25] We may exploit this to engineer the magnetic properties of extremely thin functional interfaces.…”