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Exploring the unique physical properties of oxide perovskites necessitates their growth on diverse single‐crystal substrates. The thin‐film growth of perovskite SrMnO3 (SMO) has been a particular focus of research due to its emerging room‐temperature multiferroicity. Herein, the epitaxial thin films of (110)‐oriented SMO are grown on the piezoelectric (110)‐oriented (1–x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 (PMN‐PT) substrate. The effects of the thickness and oxygen annealing on the crystal structure, stoichiometry, and ferroelectric properties of the SMO thin film are systematically investigated. The tensile strain produced by the lattice mismatch between the bulk SMO and the PMN‐PT substrate causes an expansion of the c‐lattice parallel to the in‐plane direction of the substrate. The films show larger a‐, b‐, and c‐lattice parameters than the bulk material, resulting in volume expansion of the unit cell. This lattice expansion is attributed to the generation of oxygen vacancies driven by the reduced formation energy caused by the high elastic strain. Piezoelectric force microscopy reveals that the SMO film contains domains with strain‐mediated in‐plane and vacancy‐mediated out‐of‐plane polarization. Furthermore, the piezoelectric response of the PMN‐PT substrate effectively modulates the biaxial tensile strain in the SMO film, offering a potential strategy for controlling the crystal structure and ferroelectric properties of SMO. [ABSTRACT FROM AUTHOR]

The discovery of ferroelectricity in HfO2 ultrathin films has gathered considerable interest from the microelectronic industry owing to their compatibility with complementary metal oxide semiconductor technology. However, a significant challenge in utilizing HfO2 thin films for commercial devices is the wakeup effect, which is an increase in polarization with the number of electric field cycles in HfO2-based capacitors. Despite efforts to develop wakeup-free HfO2 thin films, the root cause of this effect remains elusive. Some studies attribute it to the tetragonal (T) to orthorhombic (O) phase transformation, while others suggest it is due to the redistribution of oxygen vacancies within the HfO2 layer during electric field cycling. This study investigated the phase transformation dynamics and oxygen vacancy distributions in TiN/Hf0.5Zr0.5O2/TiN capacitors subjected to electric field cycling using in situ grazing incidence synchrotron x-ray diffraction and ex situ x-ray photoelectron spectroscopy. The as-grown HZO films were crystallized in a mixed phase consisting of monoclinic (M), tetragonal, and orthorhombic fractions. The T-phase volume fraction decreased continuously up to 10k electric field cycles. In contrast, the O-phase fraction increased within the first 100 cycles and then stabilized with further cycling. The redistribution of oxygen vacancies occurred continuously throughout the cycling process. The results revealed that continuous oxygen vacancy redistribution during electric field cycling resulted in phase transformation between the T-, O-, and M-phases. The study provides insight into the phase transformation dynamics and oxygen vacancy redistribution in TiN/Hf0.5Zr0.5O2/TiN capacitors during electric field cycling, shedding light on the underlying mechanisms of the wakeup effect. [ABSTRACT FROM AUTHOR]

Ferroelectric (FE) capacitors exhibiting ultrahigh power densities are widely utilized as electrostatic energy storage devices in pulsed electronic devices. One approach to maximize the discharge energy density (Ud) of capacitors is to increase the breakdown strength (Eb) accompanied with high maximum polarization (Pm) while suppressing the energy loss. However, the inverse relationship between Eb and Pm challenges the simultaneous enhancement of Eb and Ud. To overcome this limitation, FE/relaxor FE (RFE) heterostructure capacitors composed of Co‐doped BaTiO3 (BTCO) and Sn‐doped BaTiO3 (BTS) epitaxial thin film layers to decouple the Eb and Pm values are fabricated and the simultaneous enhancement of the Eb and Ud up to 7.9 MV cm−1 and 117 J cm−3, respectively is achieved. The high Eb and Ud values can be attributed to the suppression of the leakage current at the BTCO/BTS interface, a narrower hysteresis loop contributed by the BTS, and high Pm and Eb from the BTCO layer. Additionally, the BTCO/BTS heterostructure capacitors exhibit excellent fatigue endurance of up to 108 cycles and are thermal stable even at 160 °C. Through properly designing the FE and RFE layers, thermally stable and reliable FE/RFE heterostructure capacitors exhibiting high Ud and Eb can be realized. [ABSTRACT FROM AUTHOR]