Strain doping driven metal-insulator transition in LaNiO3 films

Complex oxides are fascinating materials, in which the manipulation of charge, orbital and lattice degrees of freedom leads to numerous exciting phenomena. We report here the use of He ion irradiation to control the out-of-plane lattice constant of epitaxial LaNiO3 (LNO) thin films independently without a change of the in-plane lattice constant. All the LNO films with the fluence less than 1×1015 He/cm2 exhibit metallic behaviors along with a slight resistivity upturn at low temperature, whereas the film with 2.5×1015 He/cm2 shows metallicity at high temperature and insulator-like behavior at low temperature. Further, the fitting for the temperature dependent resistance indicates that electrical-conductivity carriers are mainly scattered by electron-boson interactions rather than electron-electron interactions. These results suggest that He ion irradiation can be an alternative route to tune the functionality of complex oxides.