Published: Electro-optic Effect in Ferroelectric HfO2 Thin Films

Our paper entitled “Linear Electro-optic Effect in Ferroelectric HfO2-based Epitaxial Thin Films” has been published in Jpn. J. Appl. Phys. Rapid Communication. We found that the Y-HfO2 film showed a linear EO response, owing to its ferroelectricity. The observed results indicate that ferroelectric HfO2-based films are viable candidates for CMOS-compatible EO devices.

Citation: JJAP 60, 070905 (2021).


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Published: Enhanced FOM in PZT Nanorods for Piezoelectric Energy Harvesting

Our paper entitled “Enhanced Figure of Merit in Pb(Zr,Ti)O3 Nanorods for Piezoelectric Energy Harvesting” has been published in AIP Adv. We experimentally clarified that the effective figure of merit (FOM) of the PZT nanorod array can be enhanced by the decreased density. This approach enables us to independently control the piezoelectric and dielectric constants of materials, making it possible to lower the effective dielectric constant while maintaining the piezoelectric constant. The results indicate that piezoelectric nanorods are a prospective candidate for small-sized PEHs where the cantilever-based PEH cannot be used at a resonant frequency.

Citation: AIP Adv. 10, 105101 (2020).

Published: PST/STO Artificial Superlattice Thin Films

Our paper entitled “(Pb0.9Sr0.1)TiO3/SrTiO3 Artificial Superlattice Thin Films and Their Electromechanical Response” has been published in J. Ceram. Soc. Jpn. We grew (Pb0.9Sr0.1)TiOn/SrTiOm artificial superlattice thin films, and investigated their electromechanical response. Synchrotron XRD indicated that the film with n/m = 14/20 had a weak periodicity in the in-plane direction, which may have arisen from the ordered polar vortex arrays existing in the PST layers. All the fabricated superlattice thin films showed the electric field-induced strain, though its magnitude was smaller than that for typical ferroelectric materials.

Citation: J. Ceram. Soc. Jpn. 128, 431-435 (2020).

Published: Enhanced Intrinsic Piezoelectric Response in c-domain PZT Nanorods

Our paper entitled “Enhanced Intrinsic Piezoelectric Response in (001)-epitaxial Single c-domain Pb(Zr,Ti)O3 Nanorods” has been published in Appl. Phys. Lett. The PZT nanorods were self-assembled and grown on the substrate at an elevated oxygen pressure by PLD, and showed a complete c-domain structure. Time-resolved X-ray diffraction measurements under an applied electric field show that the fabricated PZT nanorods exhibit a piezoelectric constant, d33, that is significantly higher than that of thin PZT films and comparable to that for unclamped single-domain bulk crystals, which is thought to be due to a significant reduction in substrate clamping. The obtained results demonstrate that the self-assembled nanorods can achieve an enhanced intrinsic piezoelectric response, which makes them attractive for a range of practical applications.

Citation: Appl. Phys. Lett. 117, 042905 (2020).

Published: Theoretical Analysis of Nanogenerators with Nanorods for Piezoelectric Energy Harvesting

Our paper entitled “Theoretical Analysis of Nanogenerators with Aligned Nanorods for Piezoelectric Energy Harvesting” has been published in Sens. Mater. We theoretically analyzed nanogenerators with aligned piezoelectric nanorods. It was shown that for the same piezoelectric materials, using a rod-shaped unit will increase the piezoelectric constant d33 by 33% compared with using a film, owing to less substrate clamping. In addition, for the case of applying normal force, the aligned nanorod array can generate an output power one or more orders of magnitude higher than films within the same volume. This sort of nanogenerator will play an important role in the integration with miniaturized sensors in the off-resonant mode.

Citation: Sens. Mater. 31, 3669-3679 (2019).

Published: Large impact of strain on electro-optic effect in (Ba, Sr)TiO3 films: experiment and theoretical comparison

Our paper entitled “Large Impact of Strain on the Electro-optic Effect in (Ba, Sr)TiO3 Thin Films: Experiment and Theoretical Comparison” has been published in Appl. Phys. Lett. We experimentally clarified that the EO properties of compressively strained BST thin films are enhanced toward the phase transition temperature modified by the strain. Although the measured EO coefficient rc was less than that theoretically predicted, the experimentally observed strain effect on the EO properties is in good qualitative agreement.

This paper was was selected as a featured article.

Citation: Appl. Phys. Lett. 115, 092901 (2019).