Control of crystallization and crystal orientation of alkoxy-derived SrBi₂Ta₂O₉ thin films by ultraviolet irradiation

A 650 °C annealed thin film was found to be a single phase of SrBi₂Ta₂O₉ (SBT) and showed the c-axis orientation without ultraviolet irradiation. The crystallinity and crystal orientation of the thin films were improved by ultraviolet irradiation using an ultrahigh-pressure mercury lamp (UHPML) or a low-pressure mercury lamp (LPML) under three conditions. In particular, the crystal orientation of the 650 °C annealed thin films dramatically changed by ultraviolet irradiation using a LPML at room temperature or using an UHPML at 150 °C. The 650 °C annealed SBT thin film prepared by ultraviolet irradiation using an UHPML at 150 °C showed a remanent polarization (Pr) of 4.3 μC/cm² and a coercive electric field (E_c) of 101 kV/cm at 10 V.