Superconductivity in La-doped strontium titanate thin films

摘要

We report on the superconductivity of lanthanum-doped SrTiO_(3) thin films grown by off-axis laser ablation on LaAlO_(3), SrTiO_(3), and NdGaO_(3) substrates in oxygen partial pressures ranging from 10~(-8) T to 21 mTorr. The La/Sr doping ratio of the ablation target was 1%. The resulting films have carrier densities measured in the range of 6.5-30×10~(19) cm~(-3) independent of temperature from room temperature to 4 K and low-temperature mobilities as high as 130 cm~(2)/V s. Critical temperatures range between 356 down to about 48 mK depending on oxygen partial pressure during growth. Measurements of superconductive transitions in a magnetic field suggest a value of the electronic effective mass around 4.5 times the free electron mass.