Insulator—metal transition and the hopping transport in epitaxial Sm0.6Nd0.4NiO3 thin films

Epitaxial Sm0.6Nd0.4NiO3 thin films were grown on different substrates by pulsed laser deposition. X-ray diffraction indicates that for SLAO substrate, strain relaxation is accompanied by the creation of oxygen vacancies. The film resistivity on LaAlO3 and SrTiO3 substrates shows a clear insulator–metal transition (IMT) at 185 and 325 K, respectively, while the film is exclusively semiconducting on SrLaAlO4. At low temperatures, the conductivity of films deposited on SrLaAlO4 and SrTiO3 is described by the Mott variable-range hopping mechanism. With increasing film thickness, progressive tensile strain relaxation takes place, which in turn results in a gradual decrease in the IMT temperature.