Editorial

2 pages, 167 KiB

Open AccessEditorial

Research and Development of Ferroelectric Material

by Jan Macutkevič

Crystals 2023, 13(3), 400; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst13030400 - 25 Feb 2023

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Ferroelectric materials are widely investigated due their unique dielectric, piezoelectric, piroelectric, electrocaloric and other properties [...] Full article

(This article belongs to the Special Issue Research and Development of Ferroelectric Material)

Research

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8 pages, 3618 KiB

Open AccessArticle

DC Ionic Conductivity in KTP and Its Isomorphs: Properties, Methods for Suppression, and Its Connection to Gray Tracking

by Laura Padberg, Viktor Quiring, Adriana Bocchini, Matteo Santandrea, Uwe Gerstmann, Wolf Gero Schmidt, Christine Silberhorn and Christof Eigner

Crystals 2022, 12(10), 1359; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12101359 - 26 Sep 2022

Cited by 3 | Viewed by 1585

Abstract

We study the DC conductivity in potassium titanyl phosphate (KTiOPO₄, KTP) and its isomorphs KTiOAsO₄ (KTA) and Rb_1%K_99%TiOPO₄ (RKTP) and introduce a method by which to reduce the overall ionic conductivity in KTP by a [...] Read more.

We study the DC conductivity in potassium titanyl phosphate (KTiOPO₄, KTP) and its isomorphs KTiOAsO₄ (KTA) and Rb_1%K_99%TiOPO₄ (RKTP) and introduce a method by which to reduce the overall ionic conductivity in KTP by a potassium nitrate treatment. Furthermore, we create so-called gray tracking in KTP and investigate the ionic conductivity in theses areas. A local unintended reduction of the ionic conductivity is observed in the gray-tracked regions, which also induce additional optical absorption in the material. We show that a thermal treatment in an oxygen-rich atmosphere removes the gray tracking and brings the ionic conductivity as well as the optical transmission back to the original level. These studies can help to choose the best material and treatment for specific applications. Full article

(This article belongs to the Special Issue Research and Development of Ferroelectric Material)

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9 pages, 1369 KiB

Open AccessArticle

Pyroelectric and Ferroelectric Properties of Hafnium Oxide Doped with Si via Plasma Enhanced ALD

by Markus Neuber, Maximilian Walter Lederer, Konstantin Mertens, Thomas Kämpfe, Malte Czernohorsky and Konrad Seidel

Crystals 2022, 12(8), 1115; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12081115 - 09 Aug 2022

Cited by 4 | Viewed by 1851

Abstract

Devices based on ferroelectric hafnium oxide are of major interest for sensor and memory applications. In particular, Si-doped hafnium oxide layers are investigated for the application in the front-end-of-line due to their resilience to high thermal treatments. Due to its very confined doping [...] Read more.

Devices based on ferroelectric hafnium oxide are of major interest for sensor and memory applications. In particular, Si-doped hafnium oxide layers are investigated for the application in the front-end-of-line due to their resilience to high thermal treatments. Due to its very confined doping concentration range, Si:HfO₂ layers based on thermal atomic layer deposition often exhibited a crossflow pattern across 300 mm wafer. Here, plasma enhanced atomic layer deposition is explored as an alternative method for producing Si-doped HfO₂ layers, and their ferroelectric and pyroelectric properties are compared. Full article

(This article belongs to the Special Issue Research and Development of Ferroelectric Material)

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9 pages, 1488 KiB

Open AccessArticle

Ferroelectric Memory Based on Topological Domain Structures: A Phase Field Simulation

by Jing Huang, Pengfei Tan, Fang Wang and Bo Li

Crystals 2022, 12(6), 786; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12060786 - 29 May 2022

Cited by 2 | Viewed by 2190

Abstract

The low storage density of ferroelectric thin film memory currently limits the further application of ferroelectric memory. Topologies based on controllable ferroelectric domain structures offer opportunities to develop microelectronic devices such as high-density memories. This study uses ferroelectric topology domains in a ferroelectric [...] Read more.

The low storage density of ferroelectric thin film memory currently limits the further application of ferroelectric memory. Topologies based on controllable ferroelectric domain structures offer opportunities to develop microelectronic devices such as high-density memories. This study uses ferroelectric topology domains in a ferroelectric field-effect transistor (FeFET) structure for memory. The electrical behavior of FeFET and its flip properties under strain and electric fields are investigated using a phase-field model combined with the device equations of field-effect transistors. When the dimensionless electric field changes from −0.10 to 0.10, the memory window drops from 2.49 V to 0.6 V and the on-state current drops from 2.511 mA to 1.951 mA; the off-state current grows from 1.532 mA to 1.877 mA. External tensile stress increases the memory window and off-state current, while compressive stress decreases it. This study shows that a ferroelectric topology can be used as memory and could significantly increase the storage density of ferroelectric memory. Full article

(This article belongs to the Special Issue Research and Development of Ferroelectric Material)

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12 pages, 1319 KiB

Open AccessEditor’s ChoiceArticle

Phase Diagram of a Strained Ferroelectric Nanowire

by Maksim A. Pavlenko, Franco Di Rino, Leo Boron, Svitlana Kondovych, Anaïs Sené, Yuri A. Tikhonov, Anna G. Razumnaya, Valerii M. Vinokur, Marcelo Sepliarsky and Igor A. Lukyanchuk

Crystals 2022, 12(4), 453; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12040453 - 24 Mar 2022

Cited by 5 | Viewed by 2825

Abstract

Ferroelectric materials manifest unique dielectric, ferroelastic, and piezoelectric properties. A targeted design of ferroelectrics at the nanoscale is not only of fundamental appeal but holds the highest potential for applications. Compared to two-dimensional nanostructures such as thin films and superlattices, one-dimensional ferroelectric nanowires [...] Read more.

Ferroelectric materials manifest unique dielectric, ferroelastic, and piezoelectric properties. A targeted design of ferroelectrics at the nanoscale is not only of fundamental appeal but holds the highest potential for applications. Compared to two-dimensional nanostructures such as thin films and superlattices, one-dimensional ferroelectric nanowires are investigated to a much lesser extent. Here, we reveal a variety of the topological polarization states, particularly the vortex and helical chiral phases, in loaded ferroelectric nanowires, which enable us to complete the strain–temperature phase diagram of the one-dimensional ferroelectrics. These phases are of prime importance for optoelectronics and quantum communication technologies. Full article

(This article belongs to the Special Issue Research and Development of Ferroelectric Material)

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10 pages, 3547 KiB

Open AccessArticle

Electrical Conductivity and Dielectric Relaxation in Ag_1−xLi_xNbO₃

by Jan Macutkevic, Juras Banys and Antoni Kania

Crystals 2022, 12(2), 158; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12020158 - 21 Jan 2022

Cited by 7 | Viewed by 2659

Abstract

The broadband electrical properties of Ag_1−xLi_xNbO₃ (ALNx) ceramics (x ≤ 0.1) together with AgNbO₃ (AN) crystals were studied over a wide temperature interval of 20–800 K. For ALNx with x ≤ 0.05, a very diffused ferroelectric phase [...] Read more.

The broadband electrical properties of Ag_1−xLi_xNbO₃ (ALNx) ceramics (x ≤ 0.1) together with AgNbO₃ (AN) crystals were studied over a wide temperature interval of 20–800 K. For ALNx with x ≤ 0.05, a very diffused ferroelectric phase transition was observed. The position of the dielectric permittivity maximum in this phase transition is strongly frequency-dependent and is described well by the Vogel–Fulcher law. The freezing temperature decreases when the lithium concentration increases. Below the ferroelectric phase transition temperature, the dielectric dispersion is mainly caused by ferroelectric domain dynamics. Moreover, for ALN3 and ALN5 ceramics at very low temperatures (below 100 K), behavior typical of dipolar glasses is observed. At higher temperatures (above 650 K for ALN5), electrical conductivity effects become important. The DC conductivity increases with temperature according to the Arhenius law and the activation energy is highest in the antiferroelectric phase. Moreover, the activation energy is strongly dependent on the lithium concentration and it is greatest when x = 0.02. Full article

(This article belongs to the Special Issue Research and Development of Ferroelectric Material)

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11 pages, 2360 KiB

Open AccessArticle

Raman Response of Quantum Critical Ferroelectric Pb-Doped SrTiO₃

by Ekaterina D. Linnik, Alexey S. Mikheykin, Diego Rubi, Vladimir B. Shirokov, Daoud Mezzane, Svitlana V. Kondovych, Igor A. Lukyanchuk and Anna G. Razumnaya

Crystals 2021, 11(12), 1469; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst11121469 - 26 Nov 2021

Cited by 4 | Viewed by 2122

Abstract

A quantum paraelectric SrTiO₃ is a material situated in close proximity to a quantum critical point (QCP) of ferroelectric transition in which the critical temperature to the ferroelectric state is suppressed down to 0 K. However, the understanding of the behavior of [...] Read more.

A quantum paraelectric SrTiO₃ is a material situated in close proximity to a quantum critical point (QCP) of ferroelectric transition in which the critical temperature to the ferroelectric state is suppressed down to 0 K. However, the understanding of the behavior of the phase transition in the vicinity of this point remains challenging. Using the concentration x of Pb in solid solution Sr_1−xPb_xTiO₃ (PSTx) as a tuning parameter and applying the combination of Raman and dielectric spectroscopy methods, we approach the QCP in PSTx and study the interplay of classical and quantum phenomena in the region of criticality. We obtain the critical temperature of PSTx and the evolution of the temperature-dependent dynamical properties of the system as a function of x to reveal the mechanism of the transition. We show that the ferroelectric transition occurs gradually through the emergence of the polar nanoregions inside the non-polar tetragonal phase with their further expansion on cooling. We also study the ferroelastic cubic-to-tetragonal structural transition, occurring at higher temperatures, and show that its properties are almost concentration-independent and not affected by the quantum criticality. Full article

(This article belongs to the Special Issue Research and Development of Ferroelectric Material)

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24 pages, 5593 KiB

Open AccessArticle

Structural Properties and Dielectric Hysteresis of Molecular Organic Ferroelectric Grown from Different Solvents

by Elena Balashova, Aleksandr A. Levin, Alexander Fokin, Alexey Redkov and Boris Krichevtsov

Crystals 2021, 11(11), 1278; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst11111278 - 21 Oct 2021

Cited by 7 | Viewed by 1955

Abstract

A comparative analysis of crystal structure, Raman spectra, and dielectric hysteresis loops was carried out for organic ferroelectric crystals of 2-methylbenzimidazole (MBI) grown from ethanol (MBI_et), acetone (MBI_ac), deuterated acetone (MBI_d-ac), or prepared by sublimation from gas [...] Read more.

A comparative analysis of crystal structure, Raman spectra, and dielectric hysteresis loops was carried out for organic ferroelectric crystals of 2-methylbenzimidazole (MBI) grown from ethanol (MBI_et), acetone (MBI_ac), deuterated acetone (MBI_d-ac), or prepared by sublimation from gas phase (MBI_gas). Raman spectroscopy shows identical frequencies of molecular vibrations in all studied crystals, proving the same molecular structure. At the same time, a detailed analysis of the asymmetry of the powder XRD reflection profiles indicates the presence of nano-scaled regions with the same MBI symmetry and crystal structure but slightly different sizes and unit cell parameters. The formation of the MBI modifications is associated with possible penetration of solvent molecules into the voids of the MBI crystal structure. Dielectric hysteresis loops in MBI_et and MBI_d-ac crystals at room temperature demonstrate significantly different values of coercive fields E_c. Analysis of hysteresis loops within the framework of the Kolmogorov-Avrami-Ishibashi (KAI) model shows that the polarization switching in MBI_d-ac occurs much faster than in MBI_et crystals, which in the KAI model is associated with different values of the characteristic frequency ω₀ and the activation field E_a of the domains wall motion. Full article

(This article belongs to the Special Issue Research and Development of Ferroelectric Material)

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10 pages, 38284 KiB

Open AccessArticle

Impact of Thermal Treatment on the Surface of Na_0.5Bi_0.5TiO₃-Based Ceramics

by Liga Bikse, Marija Dunce, Eriks Birks, Karlis Kundzins, Otto Freimanis, Maris Livins, Jevgenijs Gabrusenoks and Andris Sternberg

Crystals 2021, 11(10), 1266; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst11101266 - 19 Oct 2021

Cited by 3 | Viewed by 1731

Abstract

Thermal etching is a widely accepted surface treatment method for studying microstructure in Na_0.5Bi_0.5TiO₃-based compositions. Surprisingly, besides the flat pattern of grains (suitable for evaluating ceramics’ microstructure), images illustrating well-expressed relief and even microstructure consisting of partly [...] Read more.

Thermal etching is a widely accepted surface treatment method for studying microstructure in Na_0.5Bi_0.5TiO₃-based compositions. Surprisingly, besides the flat pattern of grains (suitable for evaluating ceramics’ microstructure), images illustrating well-expressed relief and even microstructure consisting of partly bonded cubic-shaped grains are also found among the micrographs presented in various publications. The present paper shows that this different surface character in Eu-modified Na_0.5Bi_0.5TiO₃ can be obtained through thermal treatment across a wide range of temperatures. At higher temperatures, remarkable growth of cubic-shaped grains on the surface is observed. This growth affects the grain size distribution on the surface more than it does within the bulk of a sample. Such micrographs cannot be used to characterise the microstructure of dense ceramics. Intensive growth of TiO₂ inclusions at high thermal treatment temperatures is also observed, revealing substantial evaporation of Bi and Na from the surface of a ceramic sample, but not from its core part. Full article

(This article belongs to the Special Issue Research and Development of Ferroelectric Material)

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8 pages, 2732 KiB

Open AccessArticle

Dielectric Response of KTaO₃ Single Crystals Weakly Co-Doped with Li and Mn

by Alexander Tkach, Sebastian Zlotnik and Paula M. Vilarinho

Crystals 2021, 11(10), 1222; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst11101222 - 10 Oct 2021

Cited by 4 | Viewed by 1705

Abstract

Alkali tantalates are encouraging functional materials with versatile properties that make them potential players in microelectronics, photocatalytic processes or medicine. Here, KTaO₃ single crystals with 0.27% Li and 0.15% or 0.31% Mn contents determined by inductively coupled plasma spectroscopy analysis are studied [...] Read more.

Alkali tantalates are encouraging functional materials with versatile properties that make them potential players in microelectronics, photocatalytic processes or medicine. Here, KTaO₃ single crystals with 0.27% Li and 0.15% or 0.31% Mn contents determined by inductively coupled plasma spectroscopy analysis are studied at low temperatures using dielectric spectroscopy in a frequency range of 10²–10⁶ Hz. Both Li and Mn doping are found to induce separate low-frequency dielectric relaxations of comparable strength in KTaO₃. The relaxation dynamics follow the Arrhenius law with activation energy values of ~77 and 107 meV, attributing the relaxation origin to the dipoles formed by off-centre Li⁺_K and Mn²⁺_K ions, respectively. Full article

(This article belongs to the Special Issue Research and Development of Ferroelectric Material)

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