Deposition of LaNiO3 thin films in an atomic layer epitaxy reactor

Abstract

LaNiO ₃ thin films have been deposited in an atomic layer epitaxy (ALE) reactor, using La(thd) ₃ , Ni(thd) ₂ and ozone as reactants, thereby proving the feasibility of the ALE technique to produce films of ternary oxides. Depositions were made on Corning glass in the temperature range 150–450 °C. The growth conditions were studied and the growth rate showed a linear dependence on the number of cycles. At 400 °C the growth rate was 0.24–0.26 Å per cycle. The growth rate of the LaNiO ₃ thin films was greatly influenced by the deposition temperature but in the temperature range 215–250 °C the growth saturated at 0.08 Å cycle ^-1 independent of the deposition temperature, thus indicating an ALE window. As-deposited thin films were amorphous but crystallized when heated at 600 °C. Simultaneously the colour of the films changed from yellow–brown to black. Possible reasons for the colour changes are discussed. Resistivity measurements showed that the crystalline thin films were metallic, ρ=(5–20)×10 ^-6 Ω m. The amorphous thin films had resistivity values five orders of magnitude larger, ρ>3 Ω m. According to scanning electron microscopy (SEM) and atomic force microscopy (AFM), the films were homogeneous and dense. The surface roughness increased on crystallisation. X-Ray photoelectron spectroscopy (XPS) and magnetic susceptibility measurements were employed in order to further characterize the amorphous and crystalline thin films.