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The Growth Window of Ferroelectric Epitaxial Hf <sub/>0.5</sub> Zr <sub/>0.5</sub> O <sub/>2</sub> Thin Films
摘要： The metastable orthorhombic phase of hafnia is generally obtained in polycrystalline films, whereas in epitaxial films its formation has been much less investigated. We have grown Hf0.5Zr0.5O2 films by pulsed laser deposition and the growth window (temperature and oxygen pressure during deposition, and film thickness) for epitaxial stabilization of the ferroelectric phase is mapped. The remnant ferroelectric polarization, up to around 24 μC/cm2, depends on the amount of orthorhombic phase and strain, and increases with temperature and pressure for fixed film thickness. Leakage current decreases by increasing thickness and temperature, and particularly by reducing oxygen pressure. The coercive electric field (EC) depends on thickness (t) according the EC - t-2/3 scaling, which is observed by the first time in ferroelectric hafnia, and the scaling extends to thickness below 5 nm. The proven ability to tailor functional properties of high quality epitaxial ferroelectric Hf0.5Zr0.5O2 films paves the way towards progress in understanding their ferroelectric properties and prototyping devices.
关键词： Growth parameters,Pulsed laser deposition,Ferroelectric HfO2,Ferroelectric oxides,Epitaxial stabilization,Oxide thin films
更新于2025-09-23 15:22:29
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Epitaxial Integration on Si(001) of Ferroelectric Hf <sub/>0.5</sub> Zr <sub/>0.5</sub> O <sub/>2</sub> Capacitors with High Retention and Endurance
摘要： Epitaxial ferroelectric Hf0.5Zr0.5O2 films have been successfully integrated in a capacitor heterostructure on Si(001). The orthorhombic Hf0.5Zr0.5O2 phase, [111] out-of-plane oriented, is stabilized in the films. The films present high remnant polarization Pr close to 20 μC/cm2, rivaling with equivalent epitaxial films on single crystalline oxide substrates. Retention time is longer than 10 years for writing field of around 5 MV/cm, and the capacitors show endurance up to 109 cycles for writing voltage of around 4 MV/cm. It is found that the formation of the orthorhombic ferroelectric phase depends critically on the bottom electrode, being achieved on La0.67Sr0.33MnO3 but not on LaNiO3. The demonstration of excellent ferroelectric properties in epitaxial films of Hf0.5Zr0.5O2 on Si(001) is relevant towards fabrication of devices that require homogeneity in the nanometer scale, as well as for better understanding of the intrinsic properties of this promising ferroelectric oxide.
关键词： Oxides thin films.,Oxides on silicon,Ferroelectric HfO2,Ferroelectric oxides,Epitaxial stabilization
更新于2025-09-19 17:15:36
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Polarization-Direction Dependence of Thermodynamic Stability of Ferroelectric BiAlO <sub/>3</sub> (0001) Polar Surfaces
摘要： Polar surfaces of ferroelectric oxides are of great importance for both fundamental and practical interest. In this report, we present a theoretical study to determine the thermodynamic stability and electronic properties of ferroelectric BiAlO3(0001) surfaces. According to the calculated surface phase diagram, we predict that the equilibrium stoichiometries are distinct for the oppositely polarized BiAlO3 surfaces under the same chemical conditions. In addition to nonstoichiometry of the surface chemical compositions, we find that anomalous filling of the surface states can also result in surface metallization in order to compensate the remarkable surface polarity. Besides providing atomic-scale understanding of the BiAlO3(0001) surfaces, we also put forward the practical implications in novel magnetoelectric devices and advanced surface chemistry.
关键词： Magnetoelectric devices,Surface chemistry,Thermodynamic stability,Surface metallization,BiAlO3(0001) surfaces,Electronic properties,Ferroelectric oxides
更新于2025-09-09 09:28:46