Antiferroelectric properties of ZrO₂ ultra-thin films prepared by atomic layer deposition

Antiferroelectric (AFE) properties of ultrathin ZrO₂ films prepared by atomic layer deposition are systematically investigated with different film thicknesses and postmetallization annealing (PMA) temperatures. After wake-up, excellent AFE characteristics are observed for the ZrO₂ thickness from 5.3 to 9.5 nm through the polarization–electric field and switching current–electric field measurements. The thickness dependence and PMA temperature dependence of AFE properties and their relations to the crystalline phase are discussed. The best AFE properties, such as the largest maximum polarization and a relatively small remanent polarization, are obtained in 6 nm-thick ZrO₂ with 400 °C PMA, attributed to the existence of the highest ratio of a tetragonal phase in the film. AFE properties are relatively degraded in other thicknesses of ZrO₂ films with 400 °C PMA, which is attributable to the existence of large amounts of an amorphous phase and a monoclinic phase in 5.3 and 9.5 nm-thick ZrO₂ films, respectively. Furthermore, it is found that higher PMA temperature of 600 °C can lead to a relatively larger remanent polarization for AFE ZrO₂ due to the increase in the ratio of the orthorhombic phase in ZrO₂ films.