Strain-mediated effects of oxygen deficiency and variation in non-fermi liquid behavior of epitaxial PrNiO₃-_δ thin films.

To understand the effects of oxygen variation in combination of different strain in perovskite nickelates, three sets of PrNiO3-δ thin films (S1, S2 and S3) were deposited on (001) oriented single-crystal wafers of, respectively, SrTiO3, LSAT [(LaAlO3)0.3(Sr2TaAlO 6)0.7] and LaAlO3. Two sets of films, S1 and S2, have tensile strain whereas the films of S3 show compressive strain. For each set, two thin films of fixed thickness (5 nm) were deposited; one film was in-situ annealed in oxygen partial pressure just after deposition and another film was not annealed. The difference of oxygen stoichiometry caused a different state of epitaxial strain in the films. So, the strain was induced in the films due to lattice mismatch with substrate, which modified due oxygen deficiency. These films show non-Fermi liquid (NFL) behavior in the metallic state. The fitting parameters to power-law equation show a systematic tuning of NFL fitting parameters because of variations in strain. Our results show that, not only the lattice mismatch induced strain, but also the oxygen stoichiometry the films is another crucial parameter in changing the state of strain and hence the NFL behavior and electronic properties of perovskite nickelates.