Epitaxial LaNiO3 Thin Films Research Articles

Understanding the Role of Defective Phases on the Conductivity Behavior of Strained Epitaxial LaNiO3 Thin Films

Understanding the Role of Defective Phases on the Conductivity Behavior of Strained Epitaxial LaNiO₃ Thin Films

Effect of Lattice Strain on the Formation of Ruddlesden-Popper Faults in Heteroepitaxial LaNiO3 for Oxygen Evolution Electrocatalysis.

A great deal of research has recently been focused on Ruddlesden-Popper (RP) two-dimensional planar faults consisting of intervened [AO] monolayers in an ABO3 perovskite framework due to the structurally peculiar shear configuration. In this work, we scrutinize the effect of elastic strain on the generation behavior of RP faults, which are electrocatalytically very active sites for the oxygen evolution reaction (OER), in (001) epitaxial LaNiO3 thin films through by using two distinct single-crystal substrates with different cubic lattice parameters. Atomic-scale direct observations reveal that RP faults can be more favorably created when tensile misfit strain is exerted. Furthermore, we demonstrate that the controlled growth of thin films show notably enhanced OER activity by the RP faults. The findings in this study highlight the impact of symmetry-breaking defect formation for better oxygen electrocatalysis in perovskite oxides.

Simulation of STEM-HAADF Image Contrast of Ruddlesden–Popper Faulted LaNiO3 Thin Films

LaNiO3 (LNO) thin films are widely used as electrode materials. Yet, their properties greatly depend on such parameters as strain state and defect density. In this work, we present a detailed structural characterization of epitaxial LNO thin films grown on LaAlO3(001). A noticeable lack of contrast between La/Ni ions occurs in selected areas as seen by scanning transmission electron microscope, high-angle annular dark-field imaging (STEM-HAADF). By using atomistic modelization and image simulations, we show that this effect, rather than signaling cation interfusion or other spurious effects, results from different Ruddlesden-Popper faulted combinations with 1/2a⟨111⟩ relative displacement of defect free perovskite blocks, in the LaNiO3 perovskite

High-quality epitaxial LaNiO3 thin films on SrTiO3(100) and LaAlO3(100)

LaNiO3 thin films have been deposited by pulsed laser deposition on SrTiO3(100) and LaAlO3(100) substrates. The processing conditions have been investigated in order to optimize electrical resistivity, crystal quality, and surface morphology. Excellent properties are achieved at moderate substrate temperature and relatively low oxygen pressure, without the need for annealing. Thickness exerts an important influence on electrical transport, as the electrical resistivity increases quickly in films thicker than a few tens of nanometer. The surface of the films on LaAlO3 is very flat in all the studied thickness range, but the films on SrTiO3 develop a pattern of boundaries and even cracks as the thickness is higher. Below the critical thickness, high-quality epitaxial films with very smooth surface and low electrical resistivity are obtained under the optimum conditions of substrate temperature and oxygen pressure. The optimum processing conditions are different depending on the substrate, and control is especially critical in films deposited on SrTiO3.

Epitaxial LaNiO3 thin films: A normal metal barrier for SNS junction

Epitaxial LaNiO3 thin films have been grown on SrTiO3 and several other substrates by pulsed laser deposition. The films are observed to be metallic down to 15 K, and the temperature dependence of resistivity is similar to that of bulk LaNiO3. Epitaxial, c-axis oriented YBa2Cu3O7-x films with good superconducting properties have been grown on the LaNiO3 (100) films. I-V characteristics of the YBa2Cu3O7-x-LaNiO3 junction are linear, indicating ohmic contact between them.