Control of High Quality SrVO₃ Electrode in Oxidizing Atmosphere

Abstract

SrVO3 (SVO) is a model system for strongly correlated oxides and is highly promising as conductive layer in heterostructures. Therefore, the control of electronic properties and morphology are essential for the advanced applications. Here, the oxygen stability during and after the deposition is explored, as SVO film is expected to undergo different postdeposition thermal and atmosphere treatments during its integration in a heterostructure. Hence, the influence of oxygen stability on morphology and electrical properties of the metallic SrVO3 grown by pulsed laser deposition has been investigated. Films grown under vacuum (SrVO3− δ ) exhibit a very smooth surface while films grown under higher oxygen pressure roughen and present nanostructures at the surface. These nanostructures are found to be of Sr3V2O8 phase and their apparition can be controlled by the oxygen supply. Subsequent thermal treatments at different temperatures under same oxygen pressure prevent formation of the Sr3V2O8 phase, lead to the stoichiometric SrVO3, and thus improve the transport properties. In this study is shown the extreme sensitivity of SVO to oxygen and the conditions to obtain high quality smooth SVO films with improved electrical properties for electrode application.

Surface Characterizations and Selective Etching of Sr‐Rich Segregation on Top of SrVO3 Thin‐Films Grown by Pulsed Laser Deposition

“…In this regard, oxygen is particularly known as a crucial parameter leading for instance to the creation of a Metal Insulator Transition (MIT) in other perovskite compounds for STO, and LaNiO 3 ,,. Moreover, a previous work shows that SVO thin‐films giving the best electrical properties presented a surface covered with strongly oriented and well‐crystallized Sr 3 V 2 O 8 nanorods on top . These nanostructures are sooner found to be insulating, regarding from other works on the dielectric properties on ceramic pellets of Sr 3 V 2 O 8 ,.…”

“…Among them, metallic bulk SrVO 3 (SVO) is a normal Fermi liquid,, as it undergoes a Metal to Insulator Mott transition with thickness reduction of few unit cells,, which is still under debates and motivates many SVO‐based heterostructure's studies ,. SVO appears also as a promising candidate in functional oxide electronics and was shown to be useful for metallic electrode applications in oxide heterostructures,, for anodes in solid oxide fuel cells,, and particularly as a transparent conducting oxide (TCO) electrode ,. Nevertheless the surface of SVO is more sensitive to oxygen,, than other perovskite oxides such as SrRuO 3 .…”

“…SVO appears also as a promising candidate in functional oxide electronics and was shown to be useful for metallic electrode applications in oxide heterostructures,, for anodes in solid oxide fuel cells,, and particularly as a transparent conducting oxide (TCO) electrode ,. Nevertheless the surface of SVO is more sensitive to oxygen,, than other perovskite oxides such as SrRuO 3 . Thus, a fine study of the surface chemistry depending of its morphology is necessary in order to obtain clean interface between the metallic SVO electrode and other functional materials deposited on top of it.…”

“…An optimized and competitive SrVO 3 (SVO) thin‐film is characterized by two factors, a stoichiometric cationic ratio Sr/V equal to 1 and a high relative resistivity ratio (RRR) which is the ratio of electrical resistivity at room temperature (300 K) and the one at low temperature (2 K). State of the art SVO thin‐films grown by pulsed laser deposition (PLD) onto SrTiO 3 (STO) (100) have a RRR of 2.4, which is much lower compared to hybrid‐MBE deposition technique ,. Since PLD is a most common technique for complex oxides, process conditions to perform an efficient SVO thin‐film are taken under strong interest ,,.…”

“…However, this process gives thin‐films with higher resistivity probably resulting from lattice defects as oxygen deficiencies (denoted SrVO 3‐δ ) ,,. Furthermore, post‐annealing under oxygen atmosphere on such SVO layer cannot be applied without nanostructures segregation limiting the RRR below a maximum value of 2.3 . From this technical drawback and in order to increase the electrical properties of SVO thin‐films, two different approaches can be investigated, on one hand nanostructures need to be removed and on the other hand smooth SVO thin‐films need to be better oxidized.…”