Characteristics of multilayered barium titanate films and their effect on thin-film electroluminescent cells

In this work, we fabricated thin-film electroluminescent (TFEL) cells with a new multilayered BaTiO ₃ layer for the low-voltage-driven devices. At first, we performed the voltage accelerated breakdown testing of the multilayered BaTiO ₃ having both high dielectric constant and high breakdown strength. The time-zero-breakdown distribution is shown to be dependent on surface roughness, while the long-term failure studied by time-dependent dielectric breakdown technique at high field is dependent on the bulk characteristics, i.e., transition layer within multilayered BaTiO ₃ (m-BT) films. Second, the TFEL devices were prepared using the multilayered BaTiO ₃ as dielectric materials. We observed a decrease of turn-on voltage with increasing thickness and increase of the maximum overvoltage. Third, typical symmetric capacitance-voltage and internal charge-phosphor field characteristics were obtained for the device with thin m-BT layers. With increasing thickness of m-BT the significant asymmetry with respect to the applied voltage polarity was observed. This is a main difference as compared with the symmetric characteristics of conventional TFEL devices with low dielectric constant insulators. The experimental results indicate that a selection of the thickness of upper m-BT and their deposition process would strongly affect the interfacial characteristics as well as bulk characteristics of an as-grown ZnS:Pr,Ce layer.