Impact of oxygen plasma pulse time on atomic-layer-deposited ZrO2 antiferroelectric energy storage capacitors

Fluorite-structured antiferroelectric (AFE) dielectric capacitors have emerged as promising candidates in energy storage applications. The AFE behaviors of dielectrics generally stem from an electric field-induced phase transition. Thus, the initial phase composition in the AFE film plays an important role in determining the performance of energy storage. This work systematically investigates the impact of oxygen plasma pulse time (OPPT) on the AFE properties of atomic-layer-deposited ZrO2 films. As the OPPT increases from 3 to 5 s, the as-deposited ZrO2 film changes from an amorphous to polycrystalline state. The ratio of cubic/tetragonal phase (C/T) in the polycrystalline ZrO2 film gradually rises with increasing the OPPT from 5 to 15 s, accompanied by a gradual decrease in defect oxygen. To improve the performance of the as-deposited ZrO2 capacitors, post-annealing is performed at 450 °C for 30 min in the forming gas. It is found that the post-annealing increases the concentration of the T phase in the ZrO2 films, which reduces gradually with prolonging the OPPT. For the amorphous as-deposited ZrO2 film under an OPPT of 3 s, the post-annealing generates the largest maximum polarization (Pmax) and energy storage density, corresponding to 19.7 μC/cm2 and 34.7 J/cm3, respectively. The results indicate that the AFE properties of the ZrO2 film are determined by the T phase content, which can be modulated by the oxygen plasma dosing duration and post-annealing. Our findings provide a different perspective for improving the energy storage performance of AFE capacitors.