Influence of Cu doping and thickness on non-Fermi liquid behaviour and metallic conductance in epitaxial PrNiO₃ thin films

We have deposited two series (12 and 5 nm) of PrNi_1-x Cu_x O₃ (x = 0-0.1) thin films on (LaAlO₃)_0.3(Sr₂Al-TiO₆)_0.7 - (LSAT) single crystal substrate using pulsed laser deposition and studied the effect of Cu doping and thickness variation on the electronic properties. For series-1 (12 nm), the undoped PrNiO₃ film shows a metal-to-insulator phase transition around 100K. A fractional doping of 1.0 atomic percentage of Cu at Ni-site is able to suppress the insulating phase completely and thereby driving the system towards steady metallicity throughout the temperature range below 300 K. However, at lower dimensions in series-2 with 5 nm thickness, these effects of Cu doping and metallicity are reduced. Resistivity data of all the films fit to power law equation show non-Fermi Liquid behaviour (NFL). A switching from one type of NFL to another type has been observed due to both, Cu doping and thickness variation. Further, the fitting parameters show a systemic variation with increasing Cu content indicating that the carrier injection by even a fractional Cu doping is highly effective in bringing metallicity in the system due to band filling effects. (orig.)