Abstract
Samarium nickelate (SmNiO3) thin films were successfully synthesized on LaAlO3 and SrTiO3 substrates using pulsed-laser deposition. The Mott metal-insulator (MI) transition of the thin films is sensitive to epitaxial strain and strain relaxation. Once the strain changes from compressive to tensile, the transition temperature of the SmNiO3 samples shifts to slightly higher values. The optical conductivity reveals the strong dependence of the Drude spectral weight on the strain relaxation. Actually, compressive strain broadens the bandwidth. In contrast, tensile strain causes the effective number of free carriers to reduce which is consistent with the d-band narrowing.
Highlights
Samarium nickelate (SmNiO3) thin films were successfully synthesized on LaAlO3 and SrTiO3 substrates using pulsed-laser deposition
We examine how the strain relaxation affects the electronic properties of epitaxial SNO thin films grown on LaAlO3 (LAO, compressive) and STO as well as their optical characteristics in the UV-visible and infrared spectrum
In order to investigate the epitaxial relation between SNO and STO, x-ray diffraction (XRD) φmeasurements were performed on the (111)SNOorth/(011)LAOpc and (111)STO/(111)SNOpc reflections (Figs 1b and 2c)
Summary
Samarium nickelate (SmNiO3) thin films were successfully synthesized on LaAlO3 and SrTiO3 substrates using pulsed-laser deposition. According to the diagram proposed by Zaanen et al.[14], RNiO3 lies in the charge-transfer region in which the band gap between the nickel 3d-band and the oxygen p-band is smaller than the on-site Coulomb interaction (Udd) The change of both Ni-O-Ni bond angle and NiO length bond with increasing temperature reduces the band gap, leading to a metallic phase. The crystallization of bulk RNiO3 in the perovskite structure is normally achieved at high temperatures and oxygen pressures Another way to stabilize the nickelate phase is to use the template effect of a perovskite substrate with minimal lattice mismatch. The tensile strain induces the creation of oxygen vacancies, which leads to the annihilation of the MI transition This has been observed for example in the case of epitaxial SNO grown on
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