Effects of Cu-doping on the vibrational and electronic properties of epitaxial PrNiO3 thin films

Abstract

We have synthesized a series of epitaxial PrNi1-xCuxO3 (x = 0–0.1) thin films (12 nm) on single crystal LaAlO3 substrate by pulsed laser deposition (PLD) method and studied the effects on vibrational and electronic properties of the prepared films. Raman spectroscopy emerges as an alternate tool to indicate an increment in octahedral tilt angles due to Cu-doping. However, this change in the tilting angle does not change the overall structural symmetry in the series. For a comparative study by temperature-dependent Raman spectroscopy, two films with x = 0 (undoped) and 0.10 (maximally doped) were chosen. The presence of anisotropic Grüneisen parameter in the system indicates that Raman frequencies associated with NiO6 octahedral vibrations are more sensitive to temperature as compared to that of NiO bond stretching frequencies. Moreover, the system undergoes more thermal expansion with temperature after inclusion of Cu-doping. Temperature-dependent Raman line width fitted with Balkanski model signifies that the anharmonicity in the system increases with Cu-doping. All the films exhibit steady metallicity below 300 K. The theoretical fits to the temperature-dependent resistivity indicate the existence of Non-Fermi Liquid transport, where all fitting parameters vary depending on Cu-doping.