Antiferroelectricity in lanthanum doped zirconia without metallic capping layers and post-deposition/-metallization anneals

Abstract

We report the effects of lanthanum doping/alloying on antiferroelectric (AFE) properties of ZrO2. Starting with pure ZrO2, an increase in La doping leads to the narrowing of the AFE double hysteresis loops and an increase in the critical voltage/electric field for AFE → ferroelectric transition. At higher La contents, the polarization-voltage characteristics of doped/alloyed ZrO2 resemble that of a non-linear dielectric without any discernible AFE-type hysteresis. X-ray diffraction based analysis indicates that the increased La content while preserving the non-polar, parent AFE, tetragonal P42/nmc phase leads to a decrease in tetragonality and the (nano-)crystallite size and an increase in the unit cell volume. Furthermore, antiferroelectric behavior is obtained in the as-deposited thin films without requiring any capping metallic layers and post-deposition/-metallization anneals due to which our specific atomic layer deposition system configuration crystallizes and stabilizes the AFE tetragonal phase during growth.

Depolarization as Driving Force in Antiferroelectric Hafnia and Ferroelectric Wake-Up

“…Our theory of depolarization-induced nucleation inhibition is thus an excellent corollary to thin films that do not exhibit Kolmogorov–Avrami–Ishibashi switching but nucleation limited switching or inhomogeneous field switching. , We therefore allow the condition that the observed coercive field in a first-order ferroelectric can increase until the total field in the ferroelectric, when summed with the switching-induced depolarization field, is smaller than the back-switching field. Such depolarization-induced nucleation inhibition can further explain the shift of the observed coercive field in ZrO 2 antiferroelectrics. , …”

“…Such depolarization-induced nucleation inhibition can further explain the shift of the observed coercive field in ZrO 2 antiferroelectrics. 21,51 2.4. Ferroelectric Hysteresis with Depolarization.…”

A Janovec‐Kay‐Dunn‐Like Behavior at Thickness Scaling in Ultra‐Thin Antiferroelectric ZrO2 Films

“…[3,13] Antiferroelectric ZrO 2 thin (≈10 nm) films can be obtained through post-deposition or post-metallization annealing in N 2 atmosphere, [13] or by employing higher temperatures during atomic layer deposition (ALD) of the heterostructures. [14] The key to obtaining antiferroelectric responses therein (as opposed to paraelectricity or ferroelectricity) is to stabilize the tetragonal phase (space group P4 2 /nmc), [6,15] while partially or completely suppressing the bulk monoclinic phase (space group P2 1 /c) and other polymorphs. [6,16] Theoretical studies have suggested that the fieldinduced polar phase in ZrO 2 is an orthorhombic one, [6,17] similar to the polar phase found in HfO 2 -based ferroelectrics.…”

Antiferroelectricity in ZrO<sub>2</sub> and Ferroelectricity in Zr, Al, La Doped HfO<sub>2</sub> Nanoparticles

“…Moreover, r P is larger for La-doped compared with that of Al-doped HfO 2 NPs. There are some differences in the electric properties of ion doped HfO 2 and ZrO 2 nanostructures [43] [45] [46]. For example Yoo et al [43] observed that the dielectric constant in Al doped HfO 2 thin films undergoes a maximum whereas in Al doped ZrO 2 thin films it decreases.…”