Room temperature Mott metal-insulator transition and its systematic control in Sm_1-xCa_xNiO₃ thin films

We report an epitaxial growth and electronic transport properties of Ca-doped SmNiO₃ (Sm_1-xCa_xNiO₃, 0≤x≤0.1) thin films deposited on (001)-oriented LaAlO₃ substrates by the pulsed laser deposition method. Due to strong electron correlations of the Sm_1-xCa_xNiO₃ films, the Mott metal-insulator (MI) transition appears around 370 K, which decreases to room temperature only by the 1%-2% Ca doping, and dramatically shifts to lower temperatures by increasing the Ca content. For x0.1, the film reveals metallic conductivity down to the lowest temperature measured. In the insulating phase of x<0.04, we observe another resistivity anomaly around 200 K corresponding to an antiferromagnetic ordering of the Ni sublattice of SmNiO₃ matrix. A complete electronic phase diagram of the Sm_1-xCa _xNiO₃ thin film is unveiled by this work.