Ferroelectric properties of dysprosium-doped Bi4Ti3O12 thin films crystallized in various atmospheres

Dysprosium-doped Bi4Ti3O12 (Bi3.4Dy0.6Ti3O12 BDT) ferroelectric thin films were deposited on Pt(111)/Ti/SiO2/Si(111) substrates by chemical solution deposition (CSD) and crystallized in nitrogen, air and oxygen atmospheres, respectively. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to identify the crystal structure, the surface and cross-section morphology of the deposited ferroelectric films. The results show that the crystallization atmosphere has significant effect on determining the crystallization and ferroelectric properties of the BDT films. The film crystallized in nitrogen at a relatively low temperature of 650 °C, exhibits excellent crystallinity and ferroelctricity with a remanent polarization of 2Pr = 24.9 μC/cm2 and a coercive field of 144.5 kV/cm. While the films annealed in air and oxygen at 650 °C do not show good crystallinity and ferroelectricity until they are annealed at 700 °C. The structure evolution and ferroelectric properties of BDT thin films annealed under different temperatures (600–750 °C) were also investigated. The crystallinity of the BDT films is improved and the average grain size increases when the annealing temperature increases from 600 °C to 750 °C at an interval of 50 °C. However, the polarization of the filas is not monotonous function of the annealing temperature.