Critical field anisotropy in the antiferroelectric switching of PbZrO3 films

in APPLIED PHYSICS LETTERS (2021), 118(4),

Antiferroelectrics have been recently sparking interest due to their potential use in energy storage and electrocaloric cooling. Their main distinctive feature is antiferroelectric switching, i.e., the ... [more ▼]

Antiferroelectrics have been recently sparking interest due to their potential use in energy storage and electrocaloric cooling. Their main distinctive feature is antiferroelectric switching, i.e., the possibility to induce a phase transition to a polar phase by an electric field. Here, we investigate the switching behavior of the model antiferroelectric perovskite PbZrO3 using thin films processed by chemical solution deposition in different geometries and orientations. Both out-of-plane and in-plane switching configurations are investigated. The critical field is observed to be highly dependent on the direction of the electric field with respect to the film texture. We show that this behavior is qualitatively consistent with a phase transition to a rhombohedral polar phase. We finally estimate the importance of crystallite orientation and film texturation in the variations observed in the literature. [less ▲]

Controlling electrical and optical properties of zinc oxide thin films grown by thermal atomic layer deposition with oxygen gas

in Results in Materials (2020), 6

The preparation of ZnO thin films with controlled electrical resistivity and optical properties is often challenged by the presence of defects, such as oxygen vacancies or interstitial zinc. Here, we ... [more ▼]

The preparation of ZnO thin films with controlled electrical resistivity and optical properties is often challenged by the presence of defects, such as oxygen vacancies or interstitial zinc. Here, we investigate the material properties of ZnO polycrystalline thin films prepared by thermal Atomic Layer Deposition (ALD) with the presence of molecular oxygen pulsing during the growth. By means of structural, electrical and optical characterizations, we identify key growth parameters of this unusual ALD process. Unexpectedly, the influence of oxygen molecules on the crystallography, microstructure and morphology of ZnO films is significant from hundred-nanometers to micrometer thick film. The electrical resistivity of the films grown with oxygen gas shows a dramatic increase from 3 to 4 orders of magnitude. Additionally, photoluminescence measurements reveal that deep-level emissions caused by defects located deep in the band gap can be reduced by applying an adequate pulsing of oxygen gas during the process. Finally, we conclude with a discussion about the degree of consistency between the chemical composition, the inner strain and the optical and electrical properties of the films obtained with the different thermodynamic parameters of growth. Several hypotheses are discussed in order to understand the dominance of (002) orientation in the presence of oxygen during the ALD growth process. [less ▲]