Effects of annealing atmosphere on microstructure, electrical properties and domain structure of BiFeO3 thin films

Abstract

Bismuth ferrite thin films were prepared by sol–gel method and spin-coating technique. The effects of annealing atmosphere (air and oxygen) on the microstructure, dielectric, ferroelectric properties and domain structure of bismuth ferrite thin films have been studied systematically. The XRD and AFM results indicate that the bismuth ferrite thin films annealed in air and oxygen atmosphere are rhombohedral perovskite structure and bismuth ferrite thin films annealed in oxygen atmosphere have higher purity, better thickness uniformity and smoothness, and slightly larger grain size than that of the sample annealed in air. Bismuth ferrite annealed in oxygen atmosphere have higher dielectric constant, lower dielectric loss and much higher remnant polarization than that of the thin films annealed in air. The PFM (Piezoelectric Force Microscopy) results indicate that there are coexistence of single domain and polydomain state grains in bismuth ferrite annealed in air and oxygen atmosphere, and the single domain critical size is 80–100 and 100–110 nm respectively. Moreover, there are non-neutral domain wall (negatively charged “tail to tail” and positively charged “head to head” domain wall) in bismuth ferrite thin films annealed in air and oxygen atmosphere.