Improved conductivity of infinite-layer LaNiO2 thin films by metal organic decomposition

• LaNiO2 films were synthesized by metal organic decomposition and topotactic reduction.
• Room-temperature resistivity as low as 0.6 mΩ cm was achieved for infinite-layer LaNiO2.
• Lattice matched substrates are important in obtaining high conductivity.

Infinite-layer LaNiO2 thin films were synthesized by metal organic decomposition and subsequent topotactic reduction in hydrogen, and their transport properties were investigated. LaNiO2 is isostructural to SrCuO2, the parent compound of high-Tc Sr0.9La0.1CuO2 with Tc = 44 K, and has 3d9 configuration, which is very rare in oxides but common to high-Tc copper oxides. The bulk synthesis of LaNiO2 is not easy, but we demonstrate in this article that the thin-film synthesis of LaNiO2 is rather easy, thanks to a large-surface-to-volume ratio, which makes oxygen diffusion prompt. Our refined synthesis conditions produced highly conducting films of LaNiO2. The resistivity of the best film is as low as 640 μΩ cm at 295 K and decreases with temperature down to 230 K but it shows a gradual upturn at lower temperatures.