Realizing semiconductivity by a large bandgap tuning in Bi4Ti3O12 via inserting La1-xSrxMnO3 perovskite layers

Bismuth layer structured Aurivillius oxides have long been considered as traditional ferroelectric dielectrics, and they are feasible platforms incubating magnetic, ferroelectric, photonic, microwave, etc. properties for many important applications. It has been a longstanding challenge to achieve a certain charge carrier concentration and to narrow the bandgap in such transition metal complex oxides, yet realizing that semiconductivity is necessary for potential integration functions such as junctions in oxide optoelectronic devices. By inserting La1-xSrxMnO3 into the typical Bi4Ti3O12 ferroelectric host, we demonstrate semiconductivity and large bandgap tuning in Bi4Ti3O12-La1-xSrxMnO3 (0.3 ≤ x ≤ 0.7) solid solutions, in which a minimum resistivity value of ρ = 5021 Ω·cm and an optical bandgap value of Eg = 1.97 eV are obtained. Soft X-ray absorption spectra provide Mn and Ti charge valence states, indicating an almost constant Mn3.2+ state and an increase towards Ti4+ when raising the La/Sr ratio.