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While the influence of various fabrication parameters during deposition on the ferroelectricity of hafnium oxide has been extensively studied, the effect of different atmospheres on the actual switching process has not yet been investigated. In this work, we characterized the ferroelectric properties of undoped hafnium oxide prepared by reactive sputtering under three different atmospheres: dry oxygen/nitrogen, wet nitrogen, and vacuum conditions. We found a significant correlation between dry and wet atmospheres and resulting polarization. Specifically, we observed a direct effect on ferroelectric switching when the film was exposed to dry atmospheres and vacuum, resulting in a higher electric field necessary to initialize the wake-up effect due to an initial imprint effect. Increasing the amount of wet nitrogen during switching decreased the imprint and lowered the necessary voltage required for the wake up. We present a simple model that explains and discusses the incorporation of moisture and its resulting consequences on the ferroelectric properties of hafnium oxide. Additionally, kinetic Monte Carlo simulations showed that the addition of protons to the oxide thin film leads to a lowering of the potential and to a redistribution of protons and oxygen vacancies, which reduces the initial imprint. [ABSTRACT FROM AUTHOR]

Even though many studies on the field cycling behavior of ferroelectric hafnium oxide have recently been published, the issue is still not fully understood. The initial increase of polarization during first cycles is explained by different theoretical and empirical approaches. Field‐induced phase changes as well as oxygen vacancy diffusion from interfacial layers toward the bulk are discussed. Trapped charges as well as the mentioned oxygen vacancy diffusion might cause a shift of the hysteresis along the voltage axis called imprint. Even though various studies connect this effect to charge diffusion with progression of cycling, a final experimental proof for the origin of wake‐up and imprint is still missing. Based on the comprehensive comparative study of hafnia–zirconia and iron‐doped lead zirconate titanate ferroelectrics, it is verified that the diffusion of oxygen vacancies is the main cause for both imprint and wake‐up. Moreover, it is shown that a local seed inhibition of ferroelectric domains is most likely responsible for the reduced ferroelectric response in pristine state. [ABSTRACT FROM AUTHOR]

In this letter, Monte Carlo simulation methods were used to investigate the influence of the defect orientation and concentration on the hysteresis loop in ferroelectric thin films. The hysteresis loops were calculated by an existing Monte Carlo model. For a certain type of defect orientation, the simulations revealed an asymmetric hysteresis loop behavior, similar to hysteresis curves recorded by imprint measurements. Though these results may not directly offer a new explanation for the imprint mechanism in ferroelectric thin films, they still provide insight information about the often observed phenomenon of imprinted hysteresis loops of as-prepared thin-film capacitors. [ABSTRACT FROM AUTHOR]