Blue-light emission at room temperature from Ar$^{+}$-irradiated SrTiO$_{3}$

SrTiO$_{3}$ is a key material for fabricating oxide-based electronic devices. We found that Ar$^{+}$-irradiated, metallic SrTiO$_{3}$ crystals emit 430-nm blue-light at room temperature. Oxygen-deficient metallic SrTiO$_{3}$ thin films also show the blue-light emission. Reciprocal mapping using synchrotron x-ray radiation at SPring-8 reveals a slight elongation of the lattice parameter along the out-of-plane direction both for these samples. We, therefore, suggest that the Ar$^{+}$-irradiation introduces oxygen deficiency in the crystal surface, and that the deficiencies generate conduction carriers which wait ready for the recombination with photo-exited holes, and play an important role in the emission. It is emphasized that the emitting region could be patterned into any size and shape by combining conventional photolithography and Ar$^{+}$-milling. These new features of SrTiO$_{3}$ will open up new possibilities for the oxide-based electronic devices.