Residual Stress In BNT And PZT Ferroelectric Thin Films

Current interest in ferroelectric thin film results from the numerous potential applications in micro-electronics, micro electromechanical system (MEMS) and information storing that utilize the unique ferroelectric, dielectric, pyroelectric, electro-optic, acousto-optic, and piezoelectric properties of the material. Therefore, the preparation and properties study on the ferroelectric thin film have attracted great interests. Due to the structural misfit and thermal misfit of the thin film/substrate system and the process form high temperature to low temperature during the preparation process of thin film, residual stress will be produced inevitably. The residual stress exits in thin film may lead to the degradation, or delamination or completely failure of the thin film. In this case, the study of residual stress in ferroelectric thin film is very important. In this paper, we introduce the preparation of Bi_3.15Nd_0.85Ti₃O₁₂ (BNT) ferroelectric thin films by chemical solution deposition (CSD) method, and characterize the microstructure and ferroelectric properties of BNT thin films, mainly focus on the evaluation and analysis of residual stresses in BNT and Pb(Zr_0.52Ti_0.48)O₃ (PZT) thin films by X-ray diffraction (XRD). The main results are given as follow.BNT ferroelectric thin films were prepared by CSD method. The microstructure and ferroelectric properties of thin film prepared under different experiment parameters were characterized. Varying annealed temperature, the BNT thin film annealed at 750℃in air and 700℃in oxygen show best ferroelectric properties. While the rapid-thermal-process annealing time is less than 180 s, the increase of annealing time could effectively improve the polarization and decrease the coercive voltage. And the BNT thin film show good ferroelectric properties only when the thickness of thin film reached a certain value. The prepared thin film presents perfect electric fatigue characteristic that the P-V loop showed little change after 10⁹ cycles switching.The residual stress in BNT thin film was measured by the conventional sin²Ïˆmethod using XRD. The experiment showed that the tensile residual stress decreased with the increase of annealing temperature. The relationship between residual stress and remanent polarization of BNT thin film was discussed by the...