Influence of annealing atmosphere on polarization behaviors of Hf0.5Zr0.5O2 ferroelectric films deposited on Ti electrodes

Ferroelectric properties of HfO2-based films are reported to be largely influenced by various factors including stress, grain size and oxygen vacancies. In this study, Hf0.5Zr0.5O2 (HZO) films were deposited directly on Ti bottom electrode (Ti-BEs). The polarization switching behavior and fatigue performance exhibited notable distinctions as a result of varying oxygen vacancies in the films upon annealing under different atmosphere of N-2, air and O-2 with different annealing time. The HZO film after being annealed in air demonstrated a comparatively larger remnant polarization (Pr) value of 20.4 mu C/cm(2 )and superior fatigue performance over 108 field cycles. Furthermore, the internal mechanisms were analyzed through density functional theory (DFT) calculations. The introduction of more oxygen vacancies was observed to reduce the formation energy of o-phase and promote the enhancement of ferroelectricity. However, it should be noted that this also resulted in an increase of leakage current. Therefore, it is crucial to carefully control the concentration of oxygen vacancies, considering the overall impact on both the reliability and ferroelectricity of thin films. The results of this work can provide an effective pathway to grow HZO ferroelectric films with high performance through the control of oxygen vacancies concentration.