Influencing the structural, vibrational and electronic properties of pulsed laser deposited PrNi0.95Cu0.05O3 thin films by tuning epitaxial strain

Abstract

The variation of epitaxial strain in thin films via thickness modification is an established way for influencing the structural and transport properties in low dimensional mott materials. To understand the effect of strain on physical properties, we have prepared a series of PrNi0.95Cu0.05O3 thin films on single crystal LaAlO3 (001) substrate, with varied thickness (5 - 25 nm) using pulsed laser deposition technique. The crystallographic structure of these films is highly oriented towards the (001) axis. The c-axis lattice constant and the unit cell volume decreases with increasing thickness, and therefore, the epitaxial strain tends to partially relax. This partial relaxation of the strain causes a substantial softening of the Raman modes. Temperature-dependent Raman spectra are analyzed to estimate two key parameters, i.e., Grüneisen parameter and first-order temperature coefficient. Power-dependent Raman Spectroscopy and the above-mentioned two parameters have been used to estimate the thermal conductivity of the 25 nm thin film. Balkanski model for three phonon processes has been used to understand the anharmonic contribution in the system, which scales with thickness. The theoretical fits to the temperature-dependent resistivity plots suggest that the films exhibit non-Fermi liquid behavior.