Photoluminescent Spectrum Changes Associated With Remanent Polarization Degradation in Sub-100-nm-thick europium-doped Strontium Bismuth Tantalate Red-phosphor Thin Films

Ferroelectric europium-doped strontium bismuth tantalate (Eu-SBT) phosphors are one of promising materials in the electro-mechano-optical coupling. To provide the coupling device driving at low voltage, the crystallinity, ferroelectric and photoluminescent properties of sol-gel-derived Eu-SBT thin films were investigated in the film thickness ranging from 98 nm to 47 nm. The prepared Eu-SBT thin films exhibited the well-saturated hysteresis loop according to the polarization reversal. The remanent polarization decreased with the film thickness, however, its value of about 2 μC/cm2 was remained even when the film thickness was 47 nm. The degradation of the remanent polarization led to the changing of the photoluminescent spectrum. The emission peaks at 615 nm associated with the 5D0→7F2 transition of the Eu3+ ion was reduced in the thick Eu-SBT films, however, was enhanced in the thinner films. The sub-100-mm thick Eu-SBT films were promising candidate as red-phosphor thin film with the electro-mechano-optical coupling function.