Substrate Effect on the Structural and Electrical Properties of LaNiO3 Thin Films.

Epitaxial LaNiO₃ (LNO) thin films prepared from the sols modified with polyethyleneimine (PEI) were grown on single-crystal LaAlO₃, (LaAlO₃)_0.3(SrAlTaO₆)_0.7, and SrTiO₃ substrates, respectively, using a simple polymer assisted deposition (PAD). The epitaxial structure, surface morphologies and transport of the LNO films were studied by X-ray diffraction (θ/2θ symmetric scan, ω-scan, and in-plane φ-scan), the field emission scanning electron microscopy, and a standard dc four-probe method. It is found that, compared with that of LNO bulk, the c-axis parameter of the LNO film increases under compressive strain and decreases under tensile strain. All the LNO films exhibit metal properties in the temperature-dependent resistivity. The resistivity of the LNO films shows an increasing trend with the lattice mismatch strain changing from compressive to tensile. It is suggested that the oxygen vacancy compensated by more Ni²⁺ changed from Ni³⁺ in the film increases with the strain changing from compressive to tensile, which results in the increase of the resistivity. [ABSTRACT FROM AUTHOR]