Enhanced electron-electron correlations in nanometricSrRuO3epitaxial films

Abstract

Epitaxial and fully strained ${\mathrm{SrRuO}}_3$ thin films have been grown on ${\mathrm{SrTiO}}_3\mathrm{}\left(100\right).$ At initial stages the growth mode is three-dimensional- (3D-)like, leading to a finger-shaped structure aligned with the substrate steps and that eventually evolves into a 2D step-flow growth. We study the impact that the defect structure associated with this unique growth mode transition has on the electronic properties of the films. Detailed analysis of the transport properties of nanometric films reveals that microstructural disorder promotes a shortening of the carrier mean free path. Remarkably enough, at low temperatures, this results in a reinforcement of quantum corrections to the conductivity as predicted by recent models of disordered, strongly correlated electronic systems. This finding may provide a simple explanation for the commonly observed—in conducting oxides-resistivity minima at low temperature. Simultaneously, the ferromagnetic transition occurring at about 140 K, becomes broader as film thickness decreases down to nanometric range. The relevance of these results for the understanding of the electronic properties of disordered electronic systems and for the technological applications of ${\mathrm{SrRuO}}_3$—and other ferromagnetic and metallic oxides—is stressed.