The ferroelectricity of (Al1−xScx)N (x = 0–0.34) thin films with various thicknesses was investigated. (Al1−xScx)N films were prepared at 400 °C on (111)Pt/TiOx/SiO2/(001)Si substrates by the radio frequency dual-source reactive magnetron sputtering method using Al and Sc targets under pure N2 gas or a mixture of N2 and Ar gases. The film deposited under N2 gas showed larger remanent polarization than those under N2 + Ar mixture. Ferroelectricity was observed for films with x = 0.10–0.34 for about 140-nm-thick films deposited under N2 gas. The x = 0.22 films showed ferroelectricity down to 48 nm in thickness from the polarization–electric field curves and the positive-up-negative-down measurement. The ferroelectricity of the 9 nm-thick film also was ascertained from scanning nonlinear dielectric microscopy measurement. These results reveal that ferroelectric polarization can switch for films with much broader compositions and thicknesses than those in the previous study.
{100}c-, {110}c- and {111}c-oriented epitaxial (K, Na)NbO3 thin films were grown at 240 °C on (100)cSrRuO3//(100)SrTiO3, (110)cSrRuO3//(110)SrTiO3, and (111)cSrRuO3//(111)SrTiO3 substrates by the hydrothermal method. Their film thicknesses increased with the deposition time and then eventually saturated at longer deposition times. Their saturated film thicknesses were mainly determined by their orientation and the order was {100}c-, {110}c- and {111}c-orientation regardless of any experimental conditions. These films consisted of grains with characteristic morphologies. All of the films exhibited similar ferroelectric and piezoelectric properties irrespective of the film orientation. The remnant polarizations (Pr) and coercive fields (Ec) of the {100}c-, {110}c- and {111}c-oriented films at the maximum electric field of 500 kV cm−1 were 31 μC cm−2 and 111 kV cm−1, 27 μC cm−2 and 94 kV cm−1, and 25 μC cm−2 and 110 kV cm−1, respectively, while their effective values of piezoelectric coefficient (d33) were approximately 31–33 pm V−1. Similar films are associated with its mixed domain structure.
Y-doped HfO2 films with thicknesses of 150−1000 nm were prepared on Pt/TiO x /SiO2/Si substrates by the sputtering method and subsequent heat treatment at 800 °C. XRD analysis showed that the films consisted of an almost pure orthorhombic/tetragonal phase. Hysteresis loops originating from the ferroelectricity were observed in the polarization−electric field relationship; the remnant polarization and coercive field were about 12 μC cm−2 and 1.2 MV cm−1, respectively. Piezoelectricity was also confirmed from the strain−electric field curves for 1 μm thick films, and the apparent piezoelectric coefficient, d 33,f, near 0 MV cm−1 was estimated to be about 2.5 pm V−1. Taking account of the relatively low dielectric constant of about 23, the piezoelectric responses from 1 μm thick films prepared by the sputtering method are useful for piezoelectric microelectromechanical system applications, especially for sensor applications, since the performance of such applications is proportional not only to the piezoelectric response but also to the inverse of the relative dielectric constant.
Using a hydrothermal method, (K0.88Na0.12)NbO3 films were deposited at 240 °C on (100) cSrRuO3//(100)SrTiO3 substrates. Moreover, without any poling treatment, direct and inverse transverse piezoelectric coefficients, e31,f, near 0 kV/cm were approximately −5.0 C/m2 for the as-deposited film. This value was nearly unchanged following the application of an electric field and poling treatment, suggesting that as-deposited films are almost in a fully self-polarized state without the application of an electric field. As-deposited films with a thickness of up to 22 μm showed constant piezoelectricity without any poling treatment. The films did not crack or peel because of substrates due to the small thermal strain originating from the low deposition temperature. The figures of merit (FOM) for the vibration energy harvester [FOM = e31,f2/(ε0εr)] and sensor [FOM = e31,f/(ε0εr)] were estimated to be good at 32.8 GPa and –5.9 GV/m, respectively, primarily because of the low relative dielectric constant of ∼110. Furthermore, the piezoelectric voltage coefficient g31 [= d31/(ε0εr)] was estimated and demonstrated a high value of 0.073 Vm/N.
We prepared a stacked structure consisting of a quasi-free-standing functional oxide thin film and a ceramic piezoelectric disk and observed the effect of the piezoelectric disk deformation on the resistance of the thin film. Epitaxial V 2 O 3 films were grown by a pulsed laser deposition method on muscovite mica substrates, peeled off using Scotch tapes, and transferred onto piezoelectric elements. In this V 2 O 3 /insulator/top electrode/piezoelectronic disk/bottom electrode structure, the resistance of the V 2 O 3 film displayed a variation of 60% by sweeping the piezoelectronic disk bias. With support from x-ray diffraction measurements under an electric field, a huge gauge factor of 3 × 10 3 in the V 2 O 3 film was inferred. The sizeable resistance change in the V 2 O 3 layer is ascribed to the piezo-actuated evolution of c/a ratios, which drives the material towards an insulating phase. A memory effect on the resistance, related to the hysteretic displacement of the piezoelectric material, is also presented.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.