Tuning the metal-insulator transition temperature of Sm$_{0.5}$Nd$_{0.5}$NiO$_{3}$ thin films via strain

We have investigated the effect of substrate induced strain and film thickness on the metal-insulator transition of the correlated oxide Sm$_{0.5}$Nd$_{0.5}$NiO$_{3}$ (SNNO). We have fabricated epitaxial 3 -- 40 nm thick SNNO films on (001) LaAlO$_{3}$ (LAO), (001) SrTiO$_{3}$ (STO), and (110) NdGaO$_{3}$ (NGO) via off-axis RF magnetron sputtering. The SNNO films are atomically smooth with (001) orientation as determined by atomic force microscopy and x-ray diffraction. SNNO films grown on LAO, subject to compressive strain, exhibit a sharp metal-insulator transition at lower temperatures. Conversely, films grown on STO and NGO, subject to tensile strain, exhibit a smeared albeit above room temperature metal-insulator transition. For all substrates, we have observed that the metal-insulator transition temperature ($T_{MI})$ increases monotonically with decreasing film thickness until the electrically dead layer is reached (below 4 nm). We discuss the effect of strain and oxygen deficiencies on the T$_{MI}$ of SNNO thin films.