Effects of Ho and Ti Doping on Structural and Electrical Properties of BiFeO_3 Thin Films

摘要

Effects of Ho and Ti ions individual doping and co-doping on the structural, electrical, and ferroelectric properties of the BiFeO_3 thin films are reported. Pure BiFeO_3, (Bi_(0.9)Ho_(0.1)) FeO_3, Bi(Fe_(0.98)Ti_(0.02))O_(3+δ), and (Bi_(0.9)Ho_(0.1))(Fe_(0.98)Ti_(0.02)O_(3+δ) thin films were prepared on Pt(111)/Ti/SiO_2/Si(100) substrates by using a chemical solution deposition method. All thin films were crystallized in distorted rhombohedral structure containing no secondary or impurity phases confirmed by using an X-ray diffraction study. Changes in microstructural features, such as grain morphology and grain size distribution, for the doped samples were analyzed by a scanning electron microscopy. From the experimental results, a low electrical leakage (1.2 × 10~(-5) A/cm~2 at 100 kV) and improved ferroelectric properties, such as a large remnant polarization (2P_r) of 52 μC/cm~2 and a low coercive field (2E_c) of 886 kV/cm, were observed for the (Bi_(0.9)Ho_(0.1))(Fe_(0.98)Ti_(0.02)O_(3+δ) thin film. Fast current relaxation and stabilization observed in the (Bi_(0.9)Ho_(0.1)) (Fe_(0.98)Ti_(0.02))O_(3+δ) imply effective reduction and neutralization of charged free carriers.