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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. [ABSTRACT FROM AUTHOR]

In situ optical characterizations of metal-insulator (MI) transition have been developed in a pulsed laser deposition (PLD) chamber. It consists of associating a spectroscopic ellipsometer and an infrared camera. The first one is sensitive to modifications of the optical indexes and the second one to the emissivity changes. We focus onto the metallic LaNiO3 and the insulating SrTiO3, which present opposite electrical properties as a function of their oxygen content. Using a combinatorial synthesis approach during fabrication by PLD onto LaAlO3 substrate, we observe the evolution of the apparent temperature for different area corresponding to single LaNiO3 or SrTiO3 layers and heterostructures during reduction and reoxygenation process at constant temperature. Thus, the possibility to grow off-stochiometric samples by PLD or to reduce them by heating under high vacuum, associated to the ability of injecting controlled quantity of oxygen by pulsed valve, provide us an original tool in order to study the (MI) transition. [ABSTRACT FROM AUTHOR]

In the present work, we focus on an original study of metal-insulator transition in LaNiO (LNO) compound by IR camera mounted on a pulsed laser deposition chamber. IR thermometry is based on the measurement of the radiated energy that is a function of the surface temperature and the emissivity ( ε) of a material. Thus, at a fixed high temperature in an oxygen equilibrium state and by fixing arbitrary an emissivity value, we can follow the evolution of the 'measured temperature' linked to the change of the real emissivity value during a reduction/reoxygenation treatment. The variation of emissivity is correlated to the change in optical constants, e.g. to the conductivity measured simultaneously by an in situ spectroscopic ellipsometry. The combination of both techniques offers a convenient way to observe in situ and contactless changes from metallic to insulator behavior and vice versa. [ABSTRACT FROM AUTHOR]

LaVO 3 (LVO) is particularly interesting due to its optical band gap of around 1.1 eV, which is close to the one of silicon (1.12 eV) and can be an interesting light-absorbing material for photovoltaic and photocatalytic devices. In this context, we investigated the optical and transport properties of LaVO 3 grown on SrTiO 3 (STO) heterostructures under various growth conditions. The study of the optical properties shows significant variation in optical absorption with oxygen partial pressure during the deposition. Moreover, from the electrical point of view, the LaVO 3 /SrTiO 3 deposited at low oxygen pressure reveals a metallic behavior with high mobility conduction. However, those grown at high oxygen pressure turn into an insulator showing a metal–insulator transition. Interestingly, the optical measurements combined with electrical sheet resistance confirm that the metallic behavior originates from the diffusion of oxygen vacancies within the SrTiO 3 substrate during the deposition process of LaVO 3 layers. These results open fascinating prospects to use LaVO 3 as an efficient optical absorber for solar irradiance, whereas, the SrTiO 3 substrate could be integrated as a bottom electrode to facilitate the collection of charge carriers. As a result, LaVO 3 /SrTiO 3 system shows promising properties and might be potentially interesting for future integration in photovoltaic and photocatalytic applications. [ABSTRACT FROM AUTHOR]