Optical study of semi-metallic LaBaCo2O5 + δ epitaxial films on MgO deposited by magnetron sputtering

• Highly epitaxial LaBaCo2O5 + δ films were grown on (001) MgO substrates using magnetron sputtering.
• Optical properties of LaBaCo2O5 + δ films were experimentally studied for the first time.
• The LaBaCo2O5 + δ films deposited by magnetron sputtering were evidenced to be semi-metallic.

LaBaCo2O5 + δ (LBCO) materials are considered promising for a number of important technologies such as solid oxide fuel cells, batteries, chemical sensors, and thin-film functional devices related to giant magnetoresistance and spintronics. In this work, we report the optical properties of LBCO films, which were deposited on MgO (001) substrate by exploring the optimized growth using a radio-frequency magnetron sputtering method. The LBCO film was found having an optical response different from a typical metal or a semiconductor. The LBCO film has rather large optical absorption, which almost linearly decreases from 3.7 × 105 to 6.7 × 103 cm− 1 in the spectral range from 4.5 to 0.1 eV. The optical conductivity suggests that the LBCO films have potential for applications of optoelectronic devices, such as photodetectors and solar cells.