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1. The influence of crystallographic texture on structural and electrical properties in ferroelectric Hf _0.5 Zr _0.5 O ₂

   https://doi.org/10.1063/5.0128038  

   Lee, Younghwan; Broughton, Rachel A.; Hsain, H. Alex; Song, Seung Keun; Edgington, Patrick G.; Horgan, Madison D.; Dowden, Amy; Bednar, Amanda; Lee, Dong Hyun; Parsons, Gregory N.; et al (December 2022, Journal of Applied Physics)

   Ferroelectric (Hf,Zr)O 2 thin films have attracted increased interest from the ferroelectrics community and the semiconductor industry due to their ability to exhibit ferroelectricity at nanoscale dimensions. The properties and performance of the ferroelectric (Hf,Zr)O 2 films generally depend on various factors such as surface energy (e.g., through grain size or thickness), defects (e.g., through dopants, oxygen vacancies, or impurities), electrodes, interface quality, and preferred crystallographic orientation (also known as crystallographic texture or simply texture) of grains and/or domains. Although some factors affecting properties and performance have been studied extensively, the effects of texture on the material properties are still not understood. Here, the influence of texture of the bottom electrode and Hf 0.5 Zr 0.5 O 2 (HZO) films on properties and performance is reported. The uniqueness of this work is the use of a consistent deposition process known as Sequential, No-Atmosphere Processing (SNAP) that produces films with different preferred orientations yet minimal other differences. The results shown in this study provide both new insight on the importance of the bottom electrode texture and new fundamental processing-structure–property relationships for the HZO films. 

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2. Strengthened relaxor behavior in (1− x )Pb(Fe _0.5 Nb _0.5 )O ₃ – x BiFeO ₃

   https://doi.org/10.1039/C9TC05883D  

   Prah, Uroš; Dragomir, Mirela; Rojac, Tadej; Benčan, Andreja; Broughton, Rachel; Chung, Ching-Chang; Jones, Jacob L.; Sherbondy, Rachel; Brennecka, Geoff; Uršič, Hana (March 2020, Journal of Materials Chemistry C)

   null (Ed.)

   A systematic study of (1− x )Pb(Fe 0.5 Nb 0.5 )O 3 – x BiFeO 3 ( x = 0–0.5) was performed by combining dielectric and electromechanical measurements with structural and microstructural characterization in order to investigate the strengthening of the relaxor properties when adding BiFeO 3 into Pb(Fe 0.5 Nb 0.5 )O 3 and forming a solid solution. Pb(Fe 0.5 Nb 0.5 )O 3 crystalizes in monoclinic symmetry exhibiting ferroelectric-like polarization versus electric field ( P–E ) hysteresis loop and sub-micron-sized ferroelectric domains. Adding BiFeO 3 to Pb(Fe 0.5 Nb 0.5 )O 3 favors a pseudocubic phase and a gradual strengthening of the relaxor behavior of the prepared ceramics. This is indicated by a broadening of the peak in temperature-dependent permittivity, narrowing of P–E hysteresis loops and decreasing size of ferroelectric domains resulting in polar nanodomains for x = 0.20 composition. The relaxor behavior was additionally confirmed by Vogel–Fulcher analysis. For the x ≥ 0.30 compositions, broad high-temperature anomalies are observed in dielectric permittivity versus temperature measurements in addition to the frequency-dispersive peak located close to room temperature. These samples also exhibit pinched P–E hysteresis loops. The observed pinching is most probably related to the reorganization of polar nanoregions under the electric field as shown by synchrotron X-ray diffraction measurements as well as by piezo-response force microscopy analysis, while in part affected by the presence of charged point defects and anti-ferroelectric order, as indicated from rapid cooling experiments and high-resolution transmission electron microscopy, respectively. 

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3. Epitaxial SrTiO ₃ films with dielectric constants exceeding 25,000

   https://doi.org/10.1073/pnas.2202189119  

   Yang, Zhifei; Lee, Dooyong; Yue, Jin; Gabel, Judith; Lee, Tien-Lin; James, Richard D.; Chambers, Scott A.; Jalan, Bharat (June 2022, Proceedings of the National Academy of Sciences)

   SrTiO 3 (STO) is an incipient ferroelectric perovskite oxide for which the onset of ferroelectric order is suppressed by quantum fluctuations. This property results in a very large increase in static dielectric constant from ∼300 at room temperature to ∼20,000 at liquid He temperature in bulk single crystals. However, the low-temperature dielectric constant of epitaxial STO films is typically a few hundred to a few thousand. Here, we use all-epitaxial capacitors of the form n -STO/undoped STO/ n -STO (001) prepared by hybrid molecular beam epitaxy, to demonstrate intrinsic dielectric constants of an unstrained STO (001) film exceeding 25,000. We show that the n -STO/undoped STO interface plays a critically important role not previously considered in determining the dielectric properties that must be properly accounted for to determine the intrinsic dielectric constant. 

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4. Structural anisotropy in Sb thin films

   https://doi.org/10.1063/5.0159670  

   Adhikari, Pradip; Wijesinghe, Anuradha; Rathore, Anjali; Yoo, Timothy Jinsoo; Kim, Gyehyeon; Yeom, Sinchul; Lee, Hyoung-Taek; Mazza, Alessandro R; Sohn, Changhee; Park, Hyeong-Ryeol; et al (January 2024, APL Materials)

   Sb thin films have attracted wide interest due to their tunable band structure, topological phases, high electron mobility, and thermoelectric properties. We successfully grow epitaxial Sb thin films on a closely lattice-matched GaSb(001) surface by molecular beam epitaxy. We find a novel anisotropic directional dependence on their structural, morphological, and electronic properties. The origin of the anisotropic features is elucidated using first-principles density functional theory (DFT) calculations. The growth regime of crystalline and amorphous Sb thin films was determined by mapping the surface reconstruction phase diagram of the GaSb(001) surface under Sb2 flux, with confirmation of structural characterizations. Crystalline Sb thin films show a rhombohedral crystal structure along the rhombohedral (211) surface orientation parallel to the cubic (001) surface orientation of the GaSb substrate. At this coherent interface, Sb atoms are aligned with the GaSb lattice along the [1̄10] crystallographic direction but are not aligned well along the [110] crystallographic direction, which results in anisotropic features in reflection of high-energy electron diffraction patterns, misfit dislocation formation, surface morphology, and transport properties. Our DFT calculations show that the preferential orientation of the rhombohedral Sb (211) plane may originate from the GaSb surface, where Sb atoms align with the Ga and Sb atoms on the reconstructed surface. The formation energy calculations confirm the stability of the experimentally observed structures. Our results provide optimal film growth conditions for further studies of novel properties of Bi1−xSbx thin films with similar lattice parameters and an identical crystal structure, as well as functional heterostructures of them with III–V semiconductor layers along the (001) surface orientation, supported by a theoretical understanding of the anisotropic film orientation. 

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5. The effect of surface termination on dielectric nonlinearity in potassium sodium niobate thin films

   https://doi.org/10.1111/jace.70084  

   Hříbalová, Soňa; Akkopru‐Akgun, Betul; Trolier‐McKinstry, Susan (November 2025, Journal of the American Ceramic Society)

   Abstract The impact of alkali‐rich and alkali‐depleted surface terminations on dielectric nonlinearity and ferroelectric properties was investigated in sputtered K_0.5Na_0.5NbO₃(KNN) films. For the alkali depleted surface termination, a ∼3 nm thick amorphous interfacial layer was found near the top electrode. The presence of a non‐ferroelectric interfacial layer reduces both the net remanent (P_r) and maximum polarization (P_max) while increasing the coercive field (E_c) in the KNN films.P_maxdecreased from 31.5 to 30.3 µC/cm², likely due to the reduced electric field in the bulk of the film. The influence of the interfacial layer on dielectric properties was evaluated using a capacitor in series model. After removing the effects of the interfacial layer, the Rayleigh coefficientsε_initand α increased by 11 and 47%, respectively. The interfacial layer has more impact on irreversible domain wall motion than on reversible contributions to the relative permittivity. It is believed that this occurs because a higher concentration of defects, such as or , associated with the alkali‐depleted interfacial layer generates internal fields that pin domain walls. Alkali depleted surface terminations also produce a higher pseudo‐activation energy for polarization reversal compared to films with alkali rich terminations, with deeper potential wells in the material's energy landscape. 

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